When creating a new connection type bridge via 'nm-connection-editor' it is always offered ifname 'bridge0' regardless of whether it is already reserved or not. Offered should be the next available ifname, as it works correctly when creating a new connection type bond. Tested with nm-connection-editor-0.9.9.0-10.git20140423.fc21.x86_64.
Upstream fix: 9ba9c3e editor: fix generating interface name for new bridge connections (rh #1090575)
http://koji.fedoraproject.org/koji/buildinfo?buildID=512800
*** Bug 1090580 has been marked as a duplicate of this bug. ***
Thanks!