Pin InfluxDB to 1.8 - PR 1 of 3 - master branch

Changes pin from 1.8.4 to 1.8. This will pick up the multiple images
tagged with 1.8.5 (following on from multiple images tagged 1.8.4)
and any future 1.8.6 etc.

Author: Paraphraser

.templates/influxdb/service.yml

@@ -1,6 +1,6 @@
 influxdb:
   container_name: influxdb
-  image: "influxdb:1.8.4"
+  image: "influxdb:1.8"
   restart: unless-stopped
   ports:
     - "8086:8086"