use time in usec for rand seed

removed extra call to srand in sesue process

srsue/src/stack/rrc/rrc.cc

@@ -170,8 +170,13 @@ void rrc::init(phy_interface_rrc_lte* phy_,
   set_mac_default();
 
   measurements.init(this);
-  // set seed for rand (used in attach)
-  srand(time(NULL));
+
+  struct timeval tv;
+  gettimeofday(&tv, NULL);
+  rrc_log->info("using srand seed of %ld\n", tv.tv_usec);
+
+  // set seed (used in CHAP auth and attach)
+  srand(tv.tv_usec);
 
   running = true;
   start();

srsue/src/stack/upper/nas.cc

@@ -119,9 +119,6 @@ void nas::init(usim_interface_nas* usim_, rrc_interface_nas* rrc_, gw_interface_
     have_ctxt = true;
   }
 
-  // set seed for rand (used in CHAP auth)
-  srand(time(NULL));
-
   running = true;
 }