Ansible launcher: add -q to rsync ssh command

Since we're in control of ssh here, we get the warnings, but we
can stop them with -q.

Change-Id: I24215fc3ce3dcbe2a0ce8574fadd8d16627fbadf
diff --git a/zuul/launcher/ansiblelaunchserver.py b/zuul/launcher/ansiblelaunchserver.py
index f66b096..d11a4af 100644
--- a/zuul/launcher/ansiblelaunchserver.py
+++ b/zuul/launcher/ansiblelaunchserver.py
@@ -638,7 +638,7 @@
                 '--compress', '-rt', '--safe-links',
                 '--rsync-path="mkdir -p {dest} && rsync"',
                 '--rsh="/usr/bin/ssh -i {private_key_file} -S none '
-                '-o StrictHostKeyChecking=no"',
+                '-o StrictHostKeyChecking=no -q"',
                 '--out-format="<<CHANGED>>%i %n%L"',
                 '"{source}/"', '"{user}@{host}:{dest}"'
             ]