Add OWNCLOUD_TRUSTED_DOMAINS to the Docker example

[michaelstingl]

Needed because of this change: https://github.com/owncloud-docker/server/pull/340

Description

Add OWNCLOUD_TRUSTED_DOMAINS to the Docker example

Related Issue

https://github.com/owncloud-docker/server/pull/340

Motivation and Context

Change in the ownCloud Docker now require to configure the trusted domains

How Has This Been Tested?

Run:

docker run --rm -d \
  --name owncloud \
  -p 18080:8080 \
  -e OWNCLOUD_TRUSTED_DOMAINS=192.168.68.64 \
  -e OWNCLOUD_APPS_ENABLE=oauth2 \
  -e ADMIN_USERNAME=admin \
  -e ADMIN_PASSWORD=admin \
  owncloud/server:latest

Then check if it works with browser: http://192.168.68.64:18080/login

Screenshots (if appropriate):

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] Added an issue with details about all relevant changes in the iOS documentation repository.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [ ] Added changelog files for the fixed issues in folder changelog/unreleased