Make Heka service watch Lua dir

In this way the service will restart when the content of
/usr/share/lma_collector changes.
diff --git a/heka/_service.sls b/heka/_service.sls
index 93e543f..d2574b2 100644
--- a/heka/_service.sls
+++ b/heka/_service.sls
@@ -70,6 +70,8 @@
   service.running:
   - name: {{ service_name }}
   - enable: True
+  - watch:
+    - file: /usr/share/lma_collector
 
 {# Setup basic structure for all roles so updates can apply #}