Fix Address Group reverse url problem due to namespace renaming
in Grizzly version of Horizon.

DHC-952
The namespace for the user dashboard changed from nova to project
making url reversing fail

Change-Id: Id418d704a95b82378b6717a0d6304d7a05d8514a
Signed-off-by: Rosario Di Somma <rosario.disomma@dreamhost.com>