Update requirements-dev to point to v18.0 branch

Change-Id: I357cb15b8dd27f1a10ac11a84595375457b0975a
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/requirements-dev.in b/requirements-dev.in
index 003bca7..1f13941 100644
--- a/requirements-dev.in
+++ b/requirements-dev.in
@@ -13,6 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
--e git+https://osm.etsi.org/gerrit/osm/common.git@master#egg=osm-common
--r https://osm.etsi.org/gitweb/?p=osm/common.git;a=blob_plain;f=requirements.txt;hb=master
+-e git+https://osm.etsi.org/gerrit/osm/common.git@v18.0#egg=osm-common
+-r https://osm.etsi.org/gitweb/?p=osm/common.git;a=blob_plain;f=requirements.txt;hb=v18.0