Fix login route  #18

at the moment the login uses index.php as a rout not the /ocs path as discussed with @MorrisJobke
This is a high prio issue since this will break login for Nc11 instances but the to be used route works backward for all Nc versions and also oC8.x versions.

cc: @tobiasKaminsky - labeling it prio high to have this in beta releases soon for testing and ship it with the next feature release of the app.

Branch has been created: https://github.com/nextcloud/android-library/tree/userInfoRouteUpdate (no changes yet)