Randomize test database

CHANGELOG

@@ -2,6 +2,7 @@ v7.14.0 (unreleased)
   - Truncate commit messages after subject line in table
   - Adjust CI config to support Docker executors
   - Added Application Settings
+  - Randomize test database for CI tests
 v7.13.1
   - Fix: user could steal specific runner

script/prepare_build.sh

@@ -18,4 +18,5 @@ else
     cp config/database.yml.mysql config/database.yml
     sed -i "s/username\:.*$/username\: runner/" config/database.yml
     sed -i "s/password\:.*$/password\: 'password'/" config/database.yml
+    sed -i "s/gitlab_ci_test/gitlab_ci_test_$((RANDOM/5000))/" config/database.yml
 fi