MDL-45204 phpunit: Fixed test_localcachedir test

make_localcache_directory is the first call to make
localcache, which is already created by reset. So deleting
existing localcache directory will pass this test

lib/tests/setuplib_test.php

@@ -155,6 +155,9 @@ class core_setuplib_testcase extends advanced_testcase {
         $this->setCurrentTimeStart();
         $timestampfile = "$CFG->localcachedir/.lastpurged";
 
+        // Delete existing localcache directory, as this is testing first call
+        // to make_localcache_directory.
+        remove_dir($CFG->localcachedir, true);
         $dir = make_localcache_directory('', false);
         $this->assertSame($CFG->localcachedir, $dir);
         $this->assertFileNotExists("$CFG->localcachedir/.htaccess");