Create signing_dir for ceilometer.

Create and initialize the signing_dir for ceilometer keystone
authentication. This ensures the ceilometer to use its own PKI cache
directory for authentication and avoids the authentication error due to
the invalid cached certifications.

Change-Id: I6fbc364695ae9be800245d14fd8945d531679550
diff --git a/stack.sh b/stack.sh
index 9f734b9..8b279c1 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1219,6 +1219,7 @@
     echo_summary "Configuring Ceilometer"
     configure_ceilometer
     echo_summary "Starting Ceilometer"
+    init_ceilometer
     start_ceilometer
 fi