[zorg] Update the scheduler for the reverse iterator builder

[pzheng]

Summary

We replace the nightly scheduler for the reverse iterator builder with a
SingleBranchScheduler.

[mgrang]

LGTM.

[gkistanova]

This seems like 2 unrelated changes.
Could you split it to 2 different items, please?

[pzheng]

I have split the patch into two. Please review the other one too.
https://reviews.llvm.org/D38152

[mgrang]

LGTM.

zorg/trunk/buildbot/osuosl/master/master.cfg

c['schedulers'].append(SingleBranchScheduler(name="llgo_scheduler",
                                 "llgo"])))
 
 c['schedulers'].append(Nightly(name="aosp_scheduler",
                                builderNames=get_all_for("aosp"),
                                hour=19,
                                minute=0,
                                branch=None))
 
-c['schedulers'].append(Nightly(name="rev_iter_scheduler",
+c['schedulers'].append(SingleBranchScheduler(name="rev_iter_scheduler",
+                                             treeStableTimer=2*60,
                                              builderNames=get_all_for("rev_iter"),
-                               hour=18,
-                               minute=0,
-                               branch=None))
+                                             change_filter=depends_on(["cfe",
+                                                                       "llvm",
+                                                                       "polly"])))
 
 c['schedulers'].extend(
     config.schedulers.getSingleBranchSchedulers(c['builders'], c['schedulers'])
     )
 
 ####### PROJECT IDENTITY
 
 c['title'] = "LLVM"
 c['titleURL'] = "http://llvm.org/"
 c['buildbotURL'] = "http://lab.llvm.org:8011/"
 
 ####### DB URL
 
 c['db_url'] = "postgresql://localhost/buildmasterdb"