More fixes for the roommanager library
The latest version of the roommmanager library (revision 636b03a44c244dd47f8ae9e7d2cb204f29326442) contains a couple of additional bugfixes and improvements. The bug fixes are:
- The function roommanager_create_room() does now actually the output parameter rid to the newly created room.
- The function roommanager_reserve_room() returns a new error if the room has been already reserved.
The submodule in the student repositories have been already updated to the latest version.