ofa_neutron_agent: Simplify
AppManager: Add a convenient method to run apps
ofa_neutron_agent: Use AppManager.run_apps

No functional changes are intended.
ofa_neutron_agent: Remove unused logger instance
ofa_neutron_agent: Change the copyright notice

As a preparation to move this module to neutron repo,
change the copyright notice to the style commonly found there.

Also, add myself as co-author.