[server/test] use server config in migration
This allows a lighter initialisation (no rtag needed).
Execution of those test move from 300 secondes to 220 seconds here. A 25%
speedup
Latest changes
--------------
* table of `all latest changes`_
Links below is providing useful RQL query example.
.. _all latest changes: view?rql=Any+M%2CX+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30