Add git2lp mapping for stevedore

stackforge/stevedore uses https://launchpad.net/python-stevedore project

Change-Id: I306590af7f32c8d2751a14f9b93bd8bae6b8fb77
Replace DEVSTACK_GATE_ZEROMQ for DEVSTACK_GATE_MQ_DRIVER in jjb

This is the last patch for replace DEVSTACK_GATE_ZEROMQ for
DEVSTACK_GATE_MQ_DRIVER in order to enable the use of qpid as
a driver in replace of rabbid and zeromq. With this patch
other mq drivers can be added in the future.
Depends on changes 55829

Change-Id: I1ddf268f51b5113ffaf4c880a0aef9ae4e089d7c
Merge "Replace DEVSTACK_GATE_ZEROMQ for DEVSTACK_GATE_MQ_DRIVER in jjb"
Merge "Add git2lp mapping for stevedore"