connection: add 'double_connection_warning' test
There should be a warning printed out if you create connection name that already exists.
https://bugzilla.redhat.com/show_bug.cgi?id=1460796
@Build:nm-1-10
Due to an influx of spam, we have had to impose restrictions on new accounts. Please see this wiki page for instructions on how to get full permissions. Sorry for the inconvenience.
There should be a warning printed out if you create connection name that already exists.
https://bugzilla.redhat.com/show_bug.cgi?id=1460796
@Build:nm-1-10