proxy: unregisterVM free token

When unregisterVM is called we want to free all the tokens we register
previously, all the tokens should not be valid anymore.

Fixes: clearcontainers#66

Signed-off-by: Jose Carlos Venegas Munoz <jose.carlos.venegas.munoz@intel.com>

proxy.go

@@ -311,6 +311,11 @@ func unregisterVM(data []byte, userData interface{}, response *handlerResponse)
 	delete(proxy.vms, vm.containerID)
 	proxy.Unlock()
 
+	if err := vm.freeSessions(); err != nil {
+		response.SetErrorf("Failed to free Sessions: %s", err)
+		return
+	}
+
 	client.vm = nil
 }
 

vm.go

@@ -627,6 +627,17 @@ func (vm *vm) AllocateSession() (*ioSession, error) {
 	return session, nil
 }
 
+func (vm *vm) freeSessions() error {
+	vm.Lock()
+	defer vm.Unlock()
+	for t := range vm.tokenToSession {
+		if err := vm.freeTokenUnlocked(t); err != nil {
+			return fmt.Errorf("Failed to free session with token %s", t)
+		}
+	}
+	return nil
+}
+
 // AssociateShim associates a shim given by the triplet (token, clientID,
 // clientConn) to a vm (POD). After associating the shim, a hyper command can
 // be issued to start the process inside the VM and data can flow between shim