stop spamming devs with inappropriate promote job failures

re #2022
https://pulp.plan.io/issues/2022

ci/jobs/build-automation.yaml

@@ -125,4 +125,5 @@
           manager.build.getBuiltOn().toComputer().setTemporarilyOffline(true)
           if(manager.logContains(".*Promotion blocked.*")) {{ manager.buildUnstable() }}
       - irc-notify-all-summary
-      - email-notify-owners
+      # - email-notify-owners
+      # don't notify owners until #2022 is fixed

ci/promote-build.py

@@ -5,8 +5,8 @@
 decision is made to promote the build, copy the built packages from their staging location to
 their tested location, as determined by the release config named on the command line.
 
-If promotion is blocked for any reason, "Promotion blocked" should be printed to stdout.
-Jenkins will use that text to differentiate job failures (red ball/failure) from promotion
+If promotion is blocked for any reason, "Promotion blocked" will be printed to stdout.
+Jenkins can use that text to differentiate job failures (red ball/failure) from promotion
 criteria no being met (yellow ball/unstable). This makes it easy for folks looking at the
 job to know if the job itself worked and decided not to promote a build, or if the job is
 broken and needs developer attention.
@@ -31,7 +31,8 @@
 
 def main():
     """Parse arguments and return an exit code (e.g. 0 for success, >=1 for failure)"""
-    parser = argparse.ArgumentParser()
+    parser = argparse.ArgumentParser(
+        description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
     parser.add_argument('config', help='The name of the release config file to load')
     parser.add_argument('--job-prefix', action='append', dest='prefixes',
                         help='Prefix of jobs to wait to finish and succeed before promoting, '
@@ -57,7 +58,10 @@ def main():
 
     if not promote:
         print "Promotion blocked by check function, exiting now."
-        return 1
+        # Returning 0 here, since this is a "normal" script exit. Jenkins scripting
+        # can be used to parse the output and change the build to Unstable, if desired,
+        # based on the printing of this message, as mentioned in the script's docstring.
+        return 0
 
     # Rsync the repos from the source dir to the target dir
     # source dir trailing slash is needed: it ensures that the *contents* of the