Ansible launcher: Remove unused plugins dir

This was being set up in the jobdir, but not used.

Change-Id: I44017b0f2bbcabe4d5fde98f68c299f5f0d7247f
diff --git a/zuul/launcher/ansiblelaunchserver.py b/zuul/launcher/ansiblelaunchserver.py
index e5a8ae5..fb10553 100644
--- a/zuul/launcher/ansiblelaunchserver.py
+++ b/zuul/launcher/ansiblelaunchserver.py
@@ -93,8 +93,6 @@
         self.root = tempfile.mkdtemp()
         self.ansible_root = os.path.join(self.root, 'ansible')
         os.makedirs(self.ansible_root)
-        self.plugins_root = os.path.join(self.ansible_root, 'plugins')
-        os.makedirs(self.plugins_root)
         self.inventory = os.path.join(self.ansible_root, 'inventory')
         self.playbook = os.path.join(self.ansible_root, 'playbook')
         self.post_playbook = os.path.join(self.ansible_root, 'post_playbook')