[BUG] Jobs fail with exception when file client times out

[dwoz]

Description
Jobs fail with an exception rather than a helpful error message when file client requests time out

    The minion function caused an exception: Traceback (most recent call last):
      File "/home/dan/src/salt/salt/minion.py", line 1935, in _thread_return
        return_data = minion_instance._execute_job_function(
      File "/home/dan/src/salt/salt/minion.py", line 1894, in _execute_job_function
        return_data = self.executors[fname](opts, data, func, args, kwargs)
      File "/home/dan/src/salt/salt/loader/lazy.py", line 149, in __call__
        return self.loader.run(run_func, *args, **kwargs)
      File "/home/dan/src/salt/salt/loader/lazy.py", line 1228, in run
        return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
      File "/home/dan/src/salt/salt/loader/lazy.py", line 1243, in _run_as
        return _func_or_method(*args, **kwargs)
      File "/home/dan/src/salt/salt/executors/direct_call.py", line 10, in execute
        return func(*args, **kwargs)
      File "/home/dan/src/salt/salt/loader/lazy.py", line 149, in __call__
        return self.loader.run(run_func, *args, **kwargs)
      File "/home/dan/src/salt/salt/loader/lazy.py", line 1228, in run
        return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
      File "/home/dan/src/salt/salt/loader/lazy.py", line 1243, in _run_as
        return _func_or_method(*args, **kwargs)
      File "/home/dan/src/salt/salt/modules/state.py", line 1394, in sls
        high_, errors = st_.render_highstate({opts["saltenv"]: mods})
      File "/home/dan/src/salt/salt/state.py", line 4461, in render_highstate
        statefiles = fnmatch.filter(self.avail[saltenv], sls_match)
      File "/home/dan/src/salt/salt/state.py", line 3562, in __getitem__
        self._avail[saltenv] = self._hs.client.list_states(saltenv)
      File "/home/dan/src/salt/salt/fileclient.py", line 379, in list_states
        for path in self.file_list(saltenv):
      File "/home/dan/src/salt/salt/fileclient.py", line 1363, in file_list
        return self.channel.send(load)
      File "/home/dan/src/salt/salt/utils/asynchronous.py", line 125, in wrap
        raise exc_info[1].with_traceback(exc_info[2])
      File "/home/dan/src/salt/salt/utils/asynchronous.py", line 131, in _target
        result = io_loop.run_sync(lambda: getattr(self.obj, key)(*args, **kwargs))
      File "/home/dan/src/salt/salt/ext/tornado/ioloop.py", line 459, in run_sync
        return future_cell[0].result()
      File "/home/dan/src/salt/salt/ext/tornado/concurrent.py", line 249, in result
        raise_exc_info(self._exc_info)
      File "<string>", line 4, in raise_exc_info
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1064, in run
        yielded = self.gen.throw(*exc_info)
      File "/home/dan/src/salt/salt/channel/client.py", line 317, in send
        ret = yield self._crypted_transfer(load, timeout=timeout, raw=raw)
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1056, in run
        value = future.result()
      File "/home/dan/src/salt/salt/ext/tornado/concurrent.py", line 249, in result
        raise_exc_info(self._exc_info)
      File "<string>", line 4, in raise_exc_info
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1064, in run
        yielded = self.gen.throw(*exc_info)
      File "/home/dan/src/salt/salt/channel/client.py", line 274, in _crypted_transfer
        ret = yield _do_transfer()
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1056, in run
        value = future.result()
      File "/home/dan/src/salt/salt/ext/tornado/concurrent.py", line 249, in result
        raise_exc_info(self._exc_info)
      File "<string>", line 4, in raise_exc_info
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1064, in run
        yielded = self.gen.throw(*exc_info)
      File "/home/dan/src/salt/salt/channel/client.py", line 255, in _do_transfer
        data = yield self.transport.send(
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1056, in run
        value = future.result()
      File "/home/dan/src/salt/salt/ext/tornado/concurrent.py", line 249, in result
        raise_exc_info(self._exc_info)
      File "<string>", line 4, in raise_exc_info
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1064, in run
        yielded = self.gen.throw(*exc_info)
      File "/home/dan/src/salt/salt/transport/zeromq.py", line 915, in send
        ret = yield self.message_client.send(load, timeout=timeout)
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1056, in run
        value = future.result()
      File "/home/dan/src/salt/salt/ext/tornado/concurrent.py", line 249, in result
        raise_exc_info(self._exc_info)
      File "<string>", line 4, in raise_exc_info
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1064, in run
        yielded = self.gen.throw(*exc_info)
      File "/home/dan/src/salt/salt/transport/zeromq.py", line 625, in send
        recv = yield future
      File "/home/dan/src/salt/salt/ext/tornado/gen.py", line 1056, in run
        value = future.result()
      File "/home/dan/src/salt/salt/ext/tornado/concurrent.py", line 249, in result
        raise_exc_info(self._exc_info)
      File "<string>", line 4, in raise_exc_info
    salt.exceptions.SaltReqTimeoutError: Message timed out