Fixes 1005877. Also, an empty master file was put in refs/meta/openstack/release so that the old NOMILESTONE logic should work without weirdness now.
This reverts commit b838629877b12fa044ce237e003b9d81a88bc9d2 and
1bfc9b22fdd1b1a275e1ac7a4e773c9cb8f41ba7 - except for the builders.py change.
Change-Id: I03e02b54e8f13dccd71cc7ec5fdf5d77fa4f42c4