MDL-41198 lib: Allow PHP to generate random seed on script start

Most srand instances are removed to allow PHP to do the work.

srand was left for group randomization due to the method used.

auth/mnet/auth.php

@@ -941,7 +941,6 @@ class auth_plugin_mnet extends auth_plugin_base {
         // run the keepalive client
         $this->keepalive_client();
 
-        // admin/cron.php should have run srand for us
         $random100 = rand(0,100);
         if ($random100 < 10) {     // Approximately 10% of the time.
             // nuke olden sessions

lib/adodb/adodb.inc.php

@@ -169,11 +169,6 @@
 				die("Illegal path http:// or ftp://");
 		}
 		
-			
-		// Initialize random number generator for randomizing cache flushes
-		// -- note Since PHP 4.2.0, the seed  becomes optional and defaults to a random value if omitted.
-		 srand(((double)microtime())*1000000);
-		
 		/**
 		 * ADODB version as a string.
 		 */

lib/cronlib.php

@@ -66,7 +66,6 @@ function cron_run() {
     // Run cleanup core cron jobs, but not every time since they aren't too important.
     // These don't have a timer to reduce load, so we'll use a random number
     // to randomly choose the percentage of times we should run these jobs.
-    srand ((double) microtime() * 10000000);
     $random100 = rand(0,100);
     if ($random100 < 20) {     // Approximately 20% of the time.
         mtrace("Running clean-up tasks...");

lib/moodlelib.php

@@ -7969,7 +7969,6 @@ function unformat_float($localefloat, $strict = false) {
  */
 function swapshuffle($array) {
 
-    srand ((double) microtime() * 10000000);
     $last = count($array) - 1;
     for ($i = 0; $i <= $last; $i++) {
         $from = rand(0, $last);
@@ -8009,7 +8008,6 @@ function swapshuffle_assoc($array) {
  * @return array
  */
 function draw_rand_array($array, $draws) {
-    srand ((double) microtime() * 10000000);
 
     $return = array();
 

lib/tests/accesslib_test.php

@@ -2274,8 +2274,6 @@ class core_accesslib_testcase extends advanced_testcase {
             $userids = array_slice($userids, 0, 5);
         }
 
-        // Random time!
-        // srand(666);
         foreach ($userids as $userid) { // No guest or deleted.
             // Each user gets 0-10 random roles.
             $rcount = rand(0, 10);