Provide support for kolla dev mode in vitrage. When
'kolla_dev_mode' or 'vitrage_dev_mode' variables are
enabled, source code of vitrage project is cloned
and bind mounted.
Partially implements: blueprint mount-sources
Co-Authored-By: zhulingjie <easyzlj@gmail.com>
Change-Id: I095f2b33857abbdd0167ae52899407f2d86229d0