SimpData: fixes to a couple of parts of _find_group ISSUE=4618
SimpData: fixes to a couple of parts of _find_group ISSUE=4618

These fixes achieve the following:

1) We want the base OID of a matching group to be a prefix of the query OID,
not just something that appears somewhere inside the OID.

2) If multiple groups match, we want a most-specific OID match, not a
least-specific match.

While I was doing (2) I also took the time to streamline a two-critera
selection into a single lexicographic sort.

GlobalNOC/simp,GlobalNOC/simp,GlobalNOC/simp,GlobalNOC/simp,GlobalNOC/simp