add emacs shell-script tagging

for files that don't start with a #! or end in .sh, the added tags
are nice for emacs users to automatically switch to the right mode.

Change-Id: If4b93e106191bc744ccad8420cef20e751cdf902
diff --git a/lib/ceilometer b/lib/ceilometer
index d90694c..58cafd1 100644
--- a/lib/ceilometer
+++ b/lib/ceilometer
@@ -138,3 +138,7 @@
 
 # Restore xtrace
 $XTRACE
+
+# Local variables:
+# mode: shell-script
+# End: