net-conf: make bridge and interface name optional
net-conf: make bridge and interface name optional

Update the run-os-net-config.sh so that we make the
bridge_name and interface_name parameters (supplied by
the SoftwareConfig) optional. This allows operators to
create custom network templates to be used on roles other than
compute and controller which appear to be the only two roles which
set bridge_name and interface_name parameters.

Change-Id: I8997cf8177c1bf0e1f19de5f93dc4e81da1a951f

openstack/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,dprince/tripleo-heat-templates