test: fix the gcc diagnostics pragma

pop without push restores the commandline options. The proper way is to
push, then ignore, then pop.

And while we're at it, change the pop argument to a comment - pop ignores
the argument, but be proper about it.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
(cherry picked from commit d803f296c6)

test/signal-logging.c

@@ -150,6 +150,7 @@ number_formatting(void)
         assert(check_float_format_test(float_tests[i]));
 }
 
+#pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wformat-security"
 static void logging_format(void)
 {
@@ -378,7 +379,7 @@ static void logging_format(void)
 
 #undef read_log_msg
 }
-#pragma GCC diagnostic pop "-Wformat-security"
+#pragma GCC diagnostic pop /* "-Wformat-security" */
 
 int
 main(int argc, char **argv)