[git-llvm] Fix Python 3 workaround to print_help

[lichray]

Summary

"parser" is named "p"

[lichray]

git-llvm is gone.

llvm/utils/git-svn/git-llvm

if __name__ == '__main__':
     QUIET = args.quiet
 
     # Python3 workaround, for when not arguments are provided.
     # See https://bugs.python.org/issue16308
     try:
         func = args.func
     except AttributeError:
         # No arguments or subcommands were given.
-        parser.print_help()
-        parser.exit()
+        p.print_help()
+        p.exit()
 
     # Dispatch to the right subcommand
     args.func(args)