Open development for 2015.2.1
Open development for 2015.2.1

This matches the workflow of other projects like neutron
and should fix the following pbr-semver errors.

2015-05-20 23:29:28.302 |     ValueError: git history requires a target version of pbr.version.SemanticVersion(2015.1.2), but target version is pbr.version.SemanticVersion(2015.1.1)
2015-05-20 23:29:28.302 |     error in setup command: Error parsing /home/jenkins/workspace/gate-networking-l2gw-pep8/setup.cfg: ValueError: git history requires a target version of pbr.version.SemanticVersion(2015.1.2), but target version is pbr.version.SemanticVersion(2015.1.1)

Change-Id: Iad18695e5ce9f8a4d28708a4b214612fbb31134b

openstack/networking-l2gw,openstack/networking-l2gw