Fix URL list for steps with Dynamic Triggers

With dynamic triggers [1], when a Trigger step invokes the same
scheduler multiple times, only one link per builder was added to the
list of URLs of the step.

This patch replaces the dict for mapping builder names to build request
IDs with a list of tuples.

[1] http://docs.buildbot.net/current/manual/cfg-buildsteps.html#dynamic-trigger

master/buildbot/steps/trigger.py

@@ -181,11 +181,11 @@ class Trigger(LoggingBuildStep):
             return
 
         was_exception = was_failure = False
-        brids = {}
+        brids = []
         for was_cb, results in rclist:
             if isinstance(results, tuple):
                 results, some_brids = results
-                brids.update(some_brids)
+                brids.extend(some_brids.items())
 
             if not was_cb:
                 was_exception = True
@@ -207,7 +207,7 @@ class Trigger(LoggingBuildStep):
 
             def add_links(res):
                 # reverse the dictionary lookup for brid to builder name
-                brid_to_bn = dict((_brid, _bn) for _bn, _brid in brids.iteritems())
+                brid_to_bn = dict((bt[1], bt[0]) for bt in brids)
 
                 for was_cb, builddicts in res:
                     if was_cb:
@@ -218,7 +218,7 @@ class Trigger(LoggingBuildStep):
                             url = master.status.getURLForBuild(bn, num)
                             self.step_status.addURL("%s #%d" % (bn, num), url)
 
-            builddicts = [master.db.builds.getBuildsForRequest(br) for br in brids.values()]
+            builddicts = [master.db.builds.getBuildsForRequest(br[1]) for br in brids]
             res = yield defer.DeferredList(builddicts, consumeErrors=1)
             add_links(res)