This adds back the change to the network_cli plugin. Ths change adds
the ensure_connect decorator to the open_shell() method to make sure
the connection is valid before trying to open a shell.
The issue was due to the addition of the decorator that will call
_connect() when there is no connection. The _connect() method should
have been mocked in the test case. This commit fixes the test
case as well
Change was originally reverted in c414ded69a
dc23667cc2