Quagga: Fix code to use srandom/random

Quagga was using a mix of srand/rand and srandom/random.
Consolidate to use srandom/random which are the POSIX
versions of random number generators

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/isisd/isis_misc.c b/isisd/isis_misc.c
index 968fa05..2dfd7cc 100644
--- a/isisd/isis_misc.c
+++ b/isisd/isis_misc.c
@@ -510,7 +510,7 @@
    * most IS-IS timers are no longer than 16 bit
    */
 
-  j = 1 + (int) ((RANDOM_SPREAD * rand ()) / (RAND_MAX + 1.0));
+  j = 1 + (int) ((RANDOM_SPREAD * random ()) / (RAND_MAX + 1.0));
 
   k = timer - (timer * (100 - jitter)) / 100;