Check if network namespaces are supported

Make sure that network namespaces are supported when
installing neutron componented and use_namespaces
option is enabled. Otherwise, raise install exception.

Change-Id: I19e7e3276f99db685f3406c1924722255bf174f8
Package lock directory for neutron

This change adds /var/lock/neutron to RPM and sets neutron's
lock_path option to it instead of previous broken value.

Closes-bug: #1250917
Change-Id: I77c11f12103d9fe14c3b4050f73315d92a89dcf8
Package and start by default neutron metadata agent

We add neutron metadata agent to all personas which have neutron. To
make it actually work we generate and package service file for it and
provide configurator for it.

Closes-bug: #1250921
Change-Id: I9bb6a12ebb33e9ccce19d9406b96d2a922065ffa
Fix couple of pylint warnings

This should not change behavior.

Change-Id: Ia10ed3fc8e3546e5686b4a1440fc993c0fbfb175