git p4: fix bug when enabling tag import/export via config variables

Use Python's True, not true. Causes failure when enabling tag
import or export in "git p4" using a config option rather than
the command line.

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

@@ -1400,7 +1400,7 @@ def run(self, args):
             rebase.rebase()
 
         if gitConfig("git-p4.exportLabels", "--bool") == "true":
-            self.exportLabels = true
+            self.exportLabels = True
 
         if self.exportLabels:
             p4Labels = getP4Labels(self.depotPath)
@@ -2675,7 +2675,7 @@ def run(self, args):
                         sys.stdout.write("\n")
 
         if gitConfig("git-p4.importLabels", "--bool") == "true":
-            self.importLabels = true
+            self.importLabels = True
 
         if self.importLabels:
             p4Labels = getP4Labels(self.depotPaths)