Install bridge-utils only if needed

The package bridge-utils is useful only if we have nova-network.
If we use Quantum, we don't have to install it.

This patch provides a condition "quantum_enabled" to check before the
installation of the package.

*Note* I replaced neutron with quantum because neutron does not exists.

Fix bug #1176087

Change-Id: Iee2ecbf2023ab211d67cb9bfeb3dbc5b4bb3eb89
Signed-off-by: Paul Belanger <paul.belanger@polybeacon.com>
Merge "Install bridge-utils only if needed" into stable/grizzly