Add state reporting to the metadata agent

Need to add state reporting in order metadata agent
to appear in Neutron's agent list output

Closes-Bug: #1250369
Change-Id: I3a001e065004685d9702e817336e5d4923597791

Conflicts:
	quantum/agent/metadata/agent.py
	quantum/common/constants.py

Hyunsun: Added some fix to use this patch with Grizzly