buildbot: Rename trigger steps

The addition of the mirror step broke the links in the notification
emails, as two steps were now named "trigger". Rename these steps to
avoid the ambiguity.

buildbot/master.cfg

@@ -542,13 +542,15 @@ def make_portwatcher_factory(triggerable):
 
     if 'mirror' in config['deploy']:
         portwatcher_factory.addStep(steps.Trigger(
+            name='mirror',
             schedulerNames=['mirror'],
             set_properties={'subportlist': Property('subportlist'), 'triggered_by': make_build_url},
             waitForFinish=True,
             updateSourceStamp=True,
             doStepIf=has_subportlist))
 
     portwatcher_factory.addStep(TriggerWithPortlist(
+        name='portbuilders',
         schedulerNames=[triggerable],
         set_properties={'triggered_by': make_build_url},
         waitForFinish=True,
@@ -1084,7 +1086,7 @@ def portWatcherMessageFormatter(mode, name, build, results, master_status):
 
         # links to individual builds
         text.append('\nLinks to individual build jobs:')
-        trigger_step = [x for x in build.getSteps() if x.getName() == 'trigger'][0]
+        trigger_step = [x for x in build.getSteps() if x.getName() == 'portbuilders'][0]
         # FIXME Sorting is lexicographic and won't work properly for
         # - ports-10.11-x86_64-builder #99
         # - ports-10.11-x86_64-builder #100