Remove use_namespaces option from etc/lbaas_agent.ini

fixes bug 1201249

Remove option from ini file since it is nor registered nor used
in lbaas agent.

Change-Id: I611f794279fea4a4155309cd0668e3b9718221b1
remove "get_agents" rule in policy.json

Bug #1200933

keep the current API behaviour due to compatibility
and leave list op authz in new API version.

Change-Id: Ia0a9b8738fa8ffe913d2e2b1ef28232abb18340d
Merge "Remove use_namespaces option from etc/lbaas_agent.ini"
Merge "remove "get_agents" rule in policy.json"