MDL-55944 testing: Reduce sleep usage.

Remove sleep() and replace with waiting for a second to roll over,
this results in a simpler call the guarantee time() has moved forward

lib/phpunit/classes/advanced_testcase.php

@@ -607,4 +607,17 @@ abstract class advanced_testcase extends base_testcase {
             }
         }
     }
+
+    /**
+     * Wait for a second to roll over, ensures future calls to time() return a different result.
+     *
+     * This is implemented instead of sleep() as we do not need to wait a full second. In some cases
+     * due to calls we may wait more than sleep() would have, on average it will be less.
+     */
+    public function waitForSecond() {
+        $starttime = time();
+        while (time() == $starttime) {
+            usleep(50000);
+        }
+    }
 }