Add metavar for --fixed-ip
Add metavar for --fixed-ip

This patch adds a metavar for the --fixed-ip option so that it's
more clear that the user needs to pass in ip_address=IP_ADDR.

Fixes bug 1188889

Change-Id: I66efd444a2df52603f124637072f194497e241e2

sajuptpm/python-neutronclient-ipam,johnpbatty/python-neutronclient,huntxu/python-neutronclient,Stavitsky/python-neutronclient,citrix-openstack-build/python-neutronclient,mangelajo/python-neutronclient,CiscoSystems/python-quantumclient,vichoward/python-neutronclient,varunarya10/python-neutronclient,citrix-openstack-build/python-neutronclient,huntxu/python-neutronclient,openstack/python-neutronclient,roaet/python-neutronclient,JioCloud/python-neutronclient,Stavitsky/python-neutronclient,JioCloud/python-neutronclient,NeCTAR-RC/python-neutronclient,CiscoSystems/python-neutronclient,asadoughi/python-neutronclient,cryptickp/python-neutronclient,vichoward/python-neutronclient,venusource/python-neutronclient,Juniper/python-neutronclient,yamahata/python-tackerclient,roaet/python-neutronclient,noironetworks/python-neutronclient,cernops/python-neutronclient,varunarya10/python-neutronclient,johnpbatty/python-neutronclient,venusource/python-neutronclient,CiscoSystems/python-quantumclient,Juniper/python-neutronclient,yamahata/python-tackerclient,ntt-sic/python-neutronclient,ntt-sic/python-neutronclient,rackerlabs/rackspace-python-neutronclient,NeCTAR-RC/python-neutronclient,rackerlabs/rackspace-python-neutronclient,cernops/python-neutronclient,noironetworks/python-neutronclient,sajuptpm/python-neutronclient-ipam,eayunstack/python-neutronclient,eayunstack/python-neutronclient,vijayendrabvs/ssl-python-neutronclient,cryptickp/python-neutronclient,vijayendrabvs/ssl-python-neutronclient,mangelajo/python-neutronclient,asadoughi/python-neutronclient,openstack/python-neutronclient,CiscoSystems/python-neutronclient