Merge branch 'use-absolute-path-for-gettext-config' into 'master'

Use an absolute path for locale path in FastGettext config

See merge request !11141

config/initializers/fast_gettext.rb

-FastGettext.add_text_domain 'gitlab', path: 'locale', type: :po
+FastGettext.add_text_domain 'gitlab', path: File.join(Rails.root, 'locale'), type: :po
 FastGettext.default_text_domain = 'gitlab'
 FastGettext.default_available_locales = Gitlab::I18n.available_locales