Comment 4 for bug 1820865

I've seen that, sometimes, the test case tries to open the netspace:
   devices = ip.get_devices()
before the L3 agent closes the process to create it.

When, in the test, we check if the netspace exists, the filesystem is updated and this function returns true but we can't open yet the file. What we can do is, in the function "network_namespace_exists", add a conditional option to check if the namespace is ready to be opened.

I'll submit a patch with this change.