TT#26827 Release panel triggers jenkins jobs with branch=none

Attempt to fix problem when release panel triggers jenkins jobs
setting branch=none when tag=mrX.X.X.1, when the branch parameter
should have branch=mrX.X.X

This fix is basically the same as the one applied a few days ago in
4f4c28d92d for the file
(top)/build/utils.py which seems similar in purpose, I am not sure why
the duplicity, but this one seems to be the file mapped for the url
".../release_panel/build".

Change-Id: I04217f7f0d4a26802e4c3b808ef9732485d27edb

release_dashboard/utils/build.py

@@ -14,6 +14,7 @@
 # with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import logging
+import string
 import uuid
 import urllib
 import requests
@@ -85,6 +86,11 @@ def trigger_build(project, trigger_release=None,
     if trigger_branch_or_tag.startswith("tag/"):
         tag = trigger_branch_or_tag.split("tag/")[1]
         params['tag'] = urllib.parse.quote(tag)
+
+        # branch is like tag but removing the last element,
+        # e.g. tag=mr5.5.2.1 -> branch=mr5.5.2
+        branch = string.join(tag.split(".")[0:-1], ".")
+        params['branch'] = urllib.parse.quote(branch)
     elif trigger_branch_or_tag.startswith("branch/"):
         branch = trigger_branch_or_tag.split("branch/")[1]
         params['branch'] = urllib.parse.quote(branch)