Initialize random number generator in main

The random number generator can be initialized when MaxScale's other
systems are being initialized. This removes the need to initialized it
when the function is used for the first time.

server/core/gateway.cc

@@ -67,6 +67,7 @@
 #include <maxscale/thread.h>
 #include <maxscale/utils.h>
 #include <maxscale/version.h>
+#include <maxscale/random_jkiss.h>
 
 #include "maxscale/config.h"
 #include "maxscale/maxscale.h"
@@ -1666,6 +1667,9 @@ int main(int argc, char **argv)
         goto return_main;
     }
 
+    /** Initialize the random number generator */
+    random_jkiss_init();
+
     if (!utils_init())
     {
         const char* logerr = "Failed to initialise utility library.";