Fixed pbr install to not error out and fail if git is not installed
Fixed pbr install to not error out and fail if git is not installed

Fixed the issue where pbr was erroring out (file not found) when
running 'python setup.py egg_info' since it was trying to get the
.git directory even if git was not installed.

Closes bug 1245676

Change-Id: I31e1f86f10f18897774b49eb293aede31641db31

varunarya10/pbr,WiFast/pbr,openstack-dev/pbr,JioCloud/pbr,WiFast/pbr,redhat-openstack/pbr,JioCloud/pbr,varunarya10/pbr,redhat-openstack/pbr,openstack-dev/pbr,klmitch/pbr,klmitch/pbr,openstack-dev/pbr