Get rid of _param:influxdb_password

This parameter and influxdb_stacklight_password are redundant and they
have to be set to the same value.
diff --git a/heka/aggregator/single.yml b/heka/aggregator/single.yml
index 4b1c71f..4bef48c 100644
--- a/heka/aggregator/single.yml
+++ b/heka/aggregator/single.yml
@@ -11,7 +11,7 @@
       influxdb_port: ${_param:influxdb_port}
       influxdb_database: ${_param:influxdb_database}
       influxdb_username: ${_param:influxdb_user}
-      influxdb_password: ${_param:influxdb_password}
+      influxdb_password: ${_param:influxdb_stacklight_password}
       nagios_host: ${_param:nagios_host}
       nagios_username: ${_param:nagios_username}
       nagios_password: ${_param:nagios_password}