Update requirements-dev to use v15 for osm-common and osm-im

Change-Id: If38fa18d089f7b555070c2563c974e287f133861
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/requirements-dev.in b/requirements-dev.in
index 49324f7..df336e2 100644
--- a/requirements-dev.in
+++ b/requirements-dev.in
@@ -13,5 +13,5 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-git+https://osm.etsi.org/gerrit/osm/IM.git@master#egg=osm-im
--r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+git+https://osm.etsi.org/gerrit/osm/IM.git@v15.0#egg=osm-im
+-r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v15.0