Create sub-module to disable uid appending to username, disabled by default

Project's page says that

"johndoe@a.example.com" would be assigned username "johndoe", "johndoe@b.example.com" would be assigned "johndoe_1" and so forth.

Sadly, after update this is no longer true, instead of "johndoe" I'm getting "johndoe_666" where 666 is UID. We verified - there is no other "johndoe" on the user list.

Note: 666 is actual UID added when I encountered this problem. As a widely recognized satanistic symbol it caused some bad feelings.