container: move channel close to its writer

let the writer of the channel close it.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

libpod/container_api.go

@@ -289,8 +289,8 @@ func (c *Container) Exec(tty, privileged bool, env, cmd []string, user, workDir
 	chWait := make(chan error)
 	go func() {
 		chWait <- execCmd.Wait()
+		close(chWait)
 	}()
-	defer close(chWait)
 
 	pidFile := c.execPidPath(sessionID)
 	// 60 second seems a reasonable time to wait