[FIX] auth_crypt: encrypt all passwords at installation

When `base_crypt` was updated for v7, the auto-encryption
at installation was dropped, with user passwords only
encrypted on-demand whenever the user would connect.

It is important to encrypt all passwords immediately to
prevent password compromission for user who do not
login often or even for deactivated users who are not
allowed to login anymore.

Fixes https://bugs.launchpad.net/openobject-addons/+bug/1280152

Based on LP merge proposal by Nicolas Bessi (Camptocamp):
https://code.launchpad.net/~camptocamp/openobject-addons/improve_auth_crypt_3_please_launchpad_work-nbi/+merge/206476