test: fix flaky test-vm-timeout

Likely fix the flaky parallel/test-vm-timeout. Increase the outer
timeout in the test checking for nested timeouts with `vm` scripts
so that its firing won’t interfere with the inner timeout.

Fixes: nodejs#6727

test/parallel/test-vm-timeout.js

@@ -29,6 +29,6 @@ assert.throws(function() {
       vm.runInNewContext('while(true) {}', context, { timeout: timeout });
     }
   };
-  vm.runInNewContext('runInVM(10)', context, { timeout: 100 });
+  vm.runInNewContext('runInVM(10)', context, { timeout: 10000 });
   throw new Error('Test 5 failed');
 }, /Script execution timed out./);