Skip public HTTP URL construction for private LP branches
This backports the fix for https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1110396 from https://github.com/breezy-team/breezy/pull/253
This backports the fix for https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1110396 from https://github.com/breezy-team/breezy/pull/253