enhance mailman monitoring

- we already had a mailman check_procs when the new check was
  recently added, causing a duplicate definition

- remove the old check(s), it checked for 'mailman' being in arguments only,
  not the entire commandline, if this is combined with a lower threshold of 1
  the check will see itself (it's also a process with args mailman) and this
  should explain why the existing check never told us when mailman was down

- use --ereg-argument-array= like we do on other checks to avoid this problem,
  check parts of the entire commandline and check for exactly:

  1 mailman ctl
  8 mailman qrunners

no more and no less...

RT: 7878

Change-Id: Ib3ef872d4477c768efde58b176fbbdeab910d710
Merge "enhance mailman monitoring" into production