Init: handle multiple httpd.listenUrl entries
Init: handle multiple httpd.listenUrl entries

Before this change:
- httpd.get() would read the last entry.
- httpd.set() would set the first entry, effectively removing one entry
  but also breaking the confiugration, as Gerrit cannot listen on two
  ports at the same time.

Now, if there are multiple httpd.listenUrl entries, init will:
- validate all the entries' syntax to be parsed as URLs (not just the
  last one), and
- print a warning that interactive mode is not supported in this case
  (when invoked without --batch), and
- most importantly, leave the entries as-is allowing Gerrit to start
  with a valid configuration.

Bug: Issue 4824
Change-Id: I57fe9fe29a0fd3399024e5c196cc889650dc6892

WANdisco/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit