Don't attempt to drop admin database in spec tests

Author: alcaeus

tests/SpecTests/FunctionalTestCase.php

@@ -186,6 +186,10 @@ protected function dropTestAndOutcomeCollections()
     {
         $context = $this->getContext();
 
+        if ($context->databaseName === 'admin') {
+            return;
+        }
+
         if ($context->bucketName !== null) {
             $bucket = $context->getGridFSBucket($context->defaultWriteOptions);
             $bucket->drop();