git p4: remove unneeded cmd initialization

It confuses pylint, and is never needed.

Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -3188,7 +3188,6 @@ def main():
         printUsage(commands.keys())
         sys.exit(2)
 
-    cmd = ""
     cmdName = sys.argv[1]
     try:
         klass = commands[cmdName]