clone: teach recursive clones to respect -q

Teach 'git clone --recurse-submodules' to respect the '-q' option by
passing down the quiet flag to the process which handles cloning of
submodules.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -764,6 +764,9 @@ static int checkout(int submodule_progress)
 		if (submodule_progress)
 			argv_array_push(&args, "--progress");
 
+		if (option_verbosity < 0)
+			argv_array_push(&args, "--quiet");
+
 		err = run_command_v_opt(args.argv, RUN_GIT_CMD);
 		argv_array_clear(&args);
 	}