Un-quote metadata address if it is IPv6
Un-quote metadata address if it is IPv6

In lib/neutron-legacy, the Nova metadata host address is
un-quoted if it is IPv6, i.e. 2001:db8::1, not [2001:db8::1].
We should be doing the same in lib/neutron.

Change-Id: I80c96603a41ef9d289712ef15b464859aa9257be

nawawi/openstack,nawawi/openstack,openstack-dev/devstack,dtroyer/devstack,dtroyer/devstack,openstack-dev/devstack