Get rid of _param:influxdb_database

The StackLight database in InfluxDB is set to 'lma' by default. If one
wants to override it, it should be done in the user model.
diff --git a/heka/aggregator/cluster.yml b/heka/aggregator/cluster.yml
index 81732b3..993cb35 100644
--- a/heka/aggregator/cluster.yml
+++ b/heka/aggregator/cluster.yml
@@ -9,7 +9,7 @@
     aggregator:
       influxdb_host: ${_param:heka_influxdb_host}
       influxdb_port: ${_param:influxdb_port}
-      influxdb_database: ${_param:influxdb_database}
+      influxdb_database: lma
       influxdb_username: lma
       influxdb_password: ${_param:influxdb_stacklight_password}
       nagios_host: ${_param:nagios_host}