[REST] concurency between connection modules may lead to strange behavior.

[arcadmlafon]

All connection modules (the one using the "local" database to store the login and password, the LDAP interface or the OpenID-Connect one)) are all independent, this may lead to some undesired behaviour depending on the starting order of all these services.

[arcadmlafon]

For instance if a same login exist in two sources it is difficult to say which one will be used.

Or if an auto importation is activated then it may produce undesired try of import of an login relative to another source.

[arcadmlafon]

Duplicate #35