move dockerfile to server repo (#11374)

* move dockerfile to server and simplify

* add harcoded-mmpackage

* build docker image EE

* update jenkins file for branches

build/entrypoint.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+if [ "${1:0:1}" = '-' ]; then
+    set -- mattermost "$@"
+fi
+
+exec "$@"