Properly fix GCC build in r357867

Submitted by:	kib
Sponsored by:	The FreeBSD Foundation

tests/sys/net/randsleep.c

@@ -37,7 +37,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 
-#define RANDOM_MAX (((long)1<<31) - 1)
+#define RANDOM_MAX ((1U<<31) - 1)
 
 int main(int argc, char** argv){
 	useconds_t max_usecs, usecs;