monitoring: add check for git merging of important repos

A check for outstanding merges in the puppet tree on the puppet masters
and of mediawiki-config on the deployment masters is introduced. See
RT #1658 and #7427.

Also, some reorg of the puppetmaster module resources is done.

Change-Id: I9bd1e7ef79ef148a6c31ab3a538c2d90e70a1c5b
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>