Merge branch 'dockerfile-touchups' into 'develop'

Update Dockerfile + some touchups to docker.exs

See merge request pleroma/pleroma!1624

Dockerfile

@@ -1,4 +1,4 @@
-FROM rinpatch/elixir:1.9.0-rc.0-alpine as build
+FROM elixir:1.9-alpine as build
 
 COPY . .
 
@@ -12,7 +12,7 @@ RUN apk add git gcc g++ musl-dev make &&\
 	mkdir release &&\
 	mix release --path release
 
-FROM alpine:latest
+FROM alpine:3.9
 
 ARG HOME=/opt/pleroma
 ARG DATA=/var/lib/pleroma

config/docker.exs

@@ -10,7 +10,7 @@
   notify_email: System.get_env("NOTIFY_EMAIL"),
   limit: 5000,
   registrations_open: false,
-  dynamic_configuration: true
+  healthcheck: true
 
 config :pleroma, Pleroma.Repo,
   adapter: Ecto.Adapters.Postgres,