Blacklist x/kingbird project from sanity-check
Blacklist x/kingbird project from sanity-check

x/kingbird doens't seem to be compatible with tempest anymore
which is breaking our tempest-tox-plugin-sanity-check gate job.

Change-Id: Icdaff49bbc2ba0e59cd528d55cad6c35014b7ad0

cisco-openstack/tempest,openstack/tempest,cisco-openstack/tempest,openstack/tempest