test(mon-pages): cover the service choice filters

The label and contact conditions were added to the services filter as a
copy of the hosts one, but only the hosts side got tests. The tricky
parts carry over verbatim - the split on the first colon only, a value
prefix becoming a regex, a bare key prefix moving to the names column,
and the escaping that keeps a prefix literal - so the services copy
could drift away from the hosts one without a single test noticing.

These mirror the hosts cases one for one, which is what makes a
divergence between the two show up as a failure.

Change-Id: I18f146f1e02174fb8ecfcafdc5611bf84c4e835d