xenapi: support the session to "unix://local"
xenapi: support the session to "unix://local"

When url is "unix://local", xenapi inspector should use specific
api to create the session to xenapi.

Change-Id: I1531c4ab75be7e1d462093dff1ddf0ca4ae4808e
Closes-Bug: 1484764

openstack/ceilometer,redhat-openstack/ceilometer,idegtiarov/ceilometer,mathslinux/ceilometer,redhat-openstack/ceilometer,fabian4/ceilometer,idegtiarov/ceilometer,openstack/ceilometer,maestro-hybrid-cloud/ceilometer,maestro-hybrid-cloud/ceilometer,isyippee/ceilometer,isyippee/ceilometer,mathslinux/ceilometer,ityaptin/ceilometer,eayunstack/ceilometer,eayunstack/ceilometer,cernops/ceilometer,fabian4/ceilometer,cernops/ceilometer,ityaptin/ceilometer