libpod: do not resuse networking on start

If a container was stopped and we try to start it before we called
cleanup it tried to reuse the network which caused a panic as the pasta
code cannot deal with that. It is also never correct as the netns must
be created by the runtime in case of custom user namespaces used. As
such the proper thing is to clean the netns up first.

Also change a e2e test to report better errors. It is not directly
related to this chnage but it failed on v1 of this patch so we noticed
the ugly error message it produced. Thanks to Ed for the fix.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

libpod/container_internal_linux.go

@@ -71,6 +71,14 @@ func (c *Container) prepare() error {
 
 	go func() {
 		defer wg.Done()
+		if c.state.State == define.ContainerStateStopped {
+			// networking should not be reused after a stop
+			if err := c.cleanupNetwork(); err != nil {
+				createNetNSErr = err
+				return
+			}
+		}
+
 		// Set up network namespace if not already set up
 		noNetNS := c.state.NetNS == ""
 		if c.config.CreateNetNS && noNetNS && !c.config.PostConfigureNetNS {