match: fix re2 compability broken in 2e2699af5649

When using re2, we call test_match() instead of match() on the
compiled regex object. While match() returns a matcher object or None,
test_match() returns True or False. So since 2e2699af5649 running test
on a machine with a re2 install fails in many places.  Instead we make
the code a bit more general and everything goes back to normal.

mercurial/match.py

@@ -1288,7 +1288,7 b' def _buildregexmatch(kindpats, globsuffi'
 
         if startidx == 0:
             matcher = _rematcher(fullregexp)
-            func = lambda s: matcher(s) is not None
+            func = lambda s: bool(matcher(s))
         else:
             group = regexps[startidx:]
             allgroups.append(_joinregexes(group))