missed s prefix for interpol
deal with NPE in mergeBranch
minor cleanups
Massive cleanup of job start watcher.

Its two tasks are now cleanly separated:
  1. report to the PR commenter and the jenkins service on newly discovered jobs
     we only report on building or queued jobs if either:
       - we're reacting to a PLS REBUILD (b.force),
       - we haven't been looking that long (retryCount > 6)
     else, if we're not running in forced mode, and have been looking for a while,
     assume the build we're looking for may have ended, and consider all builds with the expected parameters
  2. try to start a job and report back when we found it on Jenkins
     on our first timeout, we try to start the build if necessary (running in force or no building/queued jobs found)
     after 12 timeouts (4 minutes), declare failure and retry the whole procedure
     when we find a building/queued job, declare victory and stop