Set HOME for the GitLab user in wrapper script

Whenever we `bundle exec` a command as the GitLab user, set the HOME
environment variable accordingly. This is the moral equivalent of the
`-H` in `sudo -u git -H bundle exec ...`.

config/templates/gitlab-rails/bundle_exec_wrapper.erb

@@ -9,5 +9,7 @@ fi
 gitlab_user=$(ls -lLd <%= install_dir %>/embedded/service/gitlab-rails/log | awk '{ print $3 }')
+export HOME=$(eval echo ~${gitlab_user})
+
 cd <%= install_dir %>/embedded/service/gitlab-rails
 exec <%= install_dir %>/embedded/bin/chpst -u $gitlab_user -U $gitlab_user <%= install_dir %>/embedded/bin/bundle exec <%= command %>