Improve scan time for some cases

When the path being matched has a sqlite wildcard character in it, a "like"
match will be quite slow. Unfortunately this is fairly common, since "_"
is a wildcard character. However, because in most cases the case of the path
in the database will match the case on disk, an "=" match will work, so it
is worthwhile to try an "=" match first, before trying a "like".

If there are no wildcard characters, the "like" will be as fast as the "=",
because of the case-insensitive index on the _data column, so there is no
need to try "=" first in that case.

b/6751354

Change-Id: I1cd4efbd56a37886cb44a86acb73eb9a3c9f303d