git p4: fix bug when verbose enabled with tag export

Wrong variable name used when verbose enabled, causes failure.

Signed-off-by: Luke Diamand <luke@diamand.org>
Acked-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -1257,7 +1257,7 @@ def exportGitTags(self, gitTags):
 
             if not m.match(name):
                 if verbose:
-                    print "tag %s does not match regexp %s" % (name, validTagRegexp)
+                    print "tag %s does not match regexp %s" % (name, validLabelRegexp)
                 continue
 
             # Get the p4 commit this corresponds to