docker: change how to check whether initial or not

[midoridge]

When gogs on docker starts for the first time, change owner of /data, /app/gogs and ~git/ to git.
The current checking way is whether /data/gogs/conf/app.ini exists or not. (refer to #5724)

But if I already prepared app.ini file before and override /data/gogs/conf/app.ini, changing owner logic is skipped.
For example, I use docker-compose.yml as the following.

version: '3'
services:
  gogs:
    depends_on:
      - mysql
    image: gogs/gogs
    hostname: gogs
    networks:
      - default
    ports:
      - "3000:3000"
      - "10022:22"
    volumes:
      - git-data:/data/
      - ./gogs/conf/app.ini:/data/gogs/conf/app.ini

So, I changed initial checking logic that owner of /data is 'git' as the following.

if [ $(stat -c '%U' /data) != 'git' ]; then

When owner of /data is not 'git', change owner of /data, /app/gogs and ~git/ to git.

[unknwon]

It is awesome! Thank you.