Add async start of the netns_command script

Change-Id: Id8b3ad7f06a13acdb49b971733b7732eb7fa6811
Fix memory corruption in ExecCmd

Change-Id: Id11fe46dc9ec96ca3d944be2b20d6bc670f8b0ac
Fix Service Type string lookup

Change-Id: Ie127470c0671302b75a34b8d3c44b3be4c5054a3
Use agent object factory to instanciate namespace_manager

Change-Id: Iae7b95db058490d97ae9079fc6b395484cb46489
Merge pull request #5 from safchain/service_instance

Add async start of the netns_command script