Ansible launcher: use sequence-uuid in shell scripts

For the generated shell scripts which are named using UUID4, prepend a
sequence count to them to easily be able to tell the ordering of the
scripts when looking in '_zuul_ansible/scripts/'.  Keep the uuid to
avoid potential collisions in /tmp.

Change-Id: Id80bf5139ba1ce12c62945421d49c5e3cd8e2f48
diff --git a/zuul/launcher/ansiblelaunchserver.py b/zuul/launcher/ansiblelaunchserver.py
index be4348a..11bcf79 100644
--- a/zuul/launcher/ansiblelaunchserver.py
+++ b/zuul/launcher/ansiblelaunchserver.py
@@ -24,6 +24,7 @@
 import threading
 import time
 import traceback
+import uuid
 import Queue
 
 import gear
@@ -1269,7 +1270,7 @@
 
     def _makeBuilderTask(self, jobdir, builder, parameters, sequence):
         tasks = []
-        script_fn = '%02d.sh' % sequence
+        script_fn = '%02d-%s.sh' % (sequence, str(uuid.uuid4().hex))
         script_path = os.path.join(jobdir.script_root, script_fn)
         with open(script_path, 'w') as script:
             data = builder['shell']