MT#55524 build: use <distribution>/master as branch instead of master

In order to support building the next supported release using the special
branch <distribution>/master if exists. Jenkins job <project>-get-code
will detect the missing branch and fallback to master if necessary

Change-Id: I798b5b1653e52e9cb4b91e9aca18cf7ec6a0916a

build/test/test_utils.py

@@ -430,7 +430,7 @@ class TriggerBuild(SimpleTestCase):
             "{base}/job/{project}/buildWithParameters?"
             "token={token}&cause={trigger_release}&uuid={uuid}&"
             "release_uuid={release_uuid}&"
-            "branch=master&tag=none&"
+            "branch={trigger_distribution}/master&tag=none&"
             "release=trunk&distribution={trigger_distribution}"
         )
         res = trigger_build(**params)

build/utils.py

@@ -159,6 +159,8 @@ def trigger_build(
         params["branch"] = urllib.parse.quote(branch)
     elif trigger_branch_or_tag.startswith("branch/"):
         branch = trigger_branch_or_tag.split("branch/")[1]
+        if branch == "master":
+            branch = f"{trigger_distribution}/master"
         params["branch"] = urllib.parse.quote(branch)
     else:
         params["branch"] = urllib.parse.quote(trigger_branch_or_tag)