Applies packstack::neutron::bridge class to network hosts

That puppet class was just applied only on compute hosts. Now it will be
applied on network hosts too.

Change-Id: I8703eccfb26bec38db82e799e0893d7e4fa5608a
Fixes: rhbz#1133968
Signed-off-by: Gael Chamoulaud <gchamoul@redhat.com>