Fix flash message shown when an account is inactive

Show different messages depending on whether the user is locked or
registered. In the latter case, also show different messages depending
on the self_registration setting (manual activation vs. mail).
Fix flash message shown when an account is inactive

Show different messages depending on whether the user is locked or
registered. In the latter case, also show different messages depending
on the self_registration setting (manual activation vs. mail).
Merge branch 'fix/flash_messages_on_inactive_account' into dev