Declare unused parameters

When building with global CFLAGS=-Wunused-parameter the output from the
build looks terrible.  This commit explicitly declares unused variables
to prevent triggering -Wunused-parameter

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/service.c

@@ -2823,6 +2823,7 @@ void service_step_all(int types)
 
 void service_worker(void *unused)
 {
+	(void)unused;
 	service_step_all(SVC_TYPE_RESPAWN | SVC_TYPE_RUNTASK);
 }