virtcontainers: wait until process exited before RemoveContainer

RemoveContainer is called right after SignalProcess(SIGKILL), the container
process might be still running and container Destroy() will fail, thus it's better
to wait on this process exited before to issue RemoveContainer.

Fixes: #690

Signed-off-by: fupan <lifupan@gmail.com>

virtcontainers/container.go

@@ -890,6 +890,12 @@ func (c *Container) stop() error {
 	// stopContainer() to succeed in such particular case.
 	c.kill(syscall.SIGKILL, true)
 
+	// Since the agent has supported the MultiWaitProcess, it's better to
+	// wait the process here to make sure the process has exited before to
+	// issue stopContainer, otherwise the RemoveContainerRequest in it will
+	// get failed if the process hasn't exited.
+	c.sandbox.agent.waitProcess(c, c.id)
+
 	if err := c.sandbox.agent.stopContainer(c.sandbox, *c); err != nil {
 		return err
 	}