Use copytruncate option for Heka log rotation

Since Heka cannot be told to close its log file and re-open it, we have
to use the copytruncate option of logrotate.

Change-Id: I8ad22f76e3c4e78a3a7a976c5a9f8fc7bc2d6dd4

deployment_scripts/puppet/modules/heka/templates/logrotate.conf.erb

@@ -1,4 +1,7 @@
 <%= @log_file %> {
     daily
     missingok
+    # Heka cannot be told to close its log file and re-open it so we need to
+    # use the copytruncate option
+    copytruncate
 }