MDL-54628 behat: Set behat dir for each run under behat_dataroot

Before this patch behat_dataroot for parallel runs
were created at same level as ->behat_dataroot
After this patch, it will be created 1 level under
->behat_dataroot with BEHAT_PARALLEL_SITE_NAME
prefix and run number as suffix. This will allow
common files as test enabled and parallel run info
to be saved in parent directory and access it easily.

lib/setup.php

@@ -84,7 +84,8 @@ if (defined('BEHAT_SITE_RUNNING')) {
     // Update config variables for parallel behat runs.
     behat_update_vars_for_process();
 
-    if (behat_is_test_site()) {
+    // If behat is being installed for parallel run, then we modify params for parallel run only.
+    if (behat_is_test_site() && !(defined('BEHAT_PARALLEL_UTIL') && empty($CFG->behatrunprocess))) {
         clearstatcache();
 
         // Checking the integrity of the provided $CFG->behat_* vars and the
@@ -116,7 +117,8 @@ if (defined('BEHAT_SITE_RUNNING')) {
 
         if (!defined('BEHAT_UTIL') and !defined('BEHAT_TEST')) {
             // Somebody tries to access test site directly, tell them if not enabled.
-            if (!file_exists($CFG->behat_dataroot . '/behat/test_environment_enabled.txt')) {
+            $behatdir = preg_replace("#[/|\\\]" . BEHAT_PARALLEL_SITE_NAME . "\d{0,}$#", '', $CFG->behat_dataroot);
+            if (!file_exists($behatdir . '/test_environment_enabled.txt')) {
                 behat_error(BEHAT_EXITCODE_CONFIG, 'Behat is configured but not enabled on this test site.');
             }
         }