If the server says in the select command that a folder
    is read-write Kontact assumes that it can modify a basic
    set of flags. (See the bug for more info) But if we can
    only modify SEEN we can reuse the setSeenFlags functions.

    This is a bit of a workaround for a proper and generic handling
    of the permanentFlags but since this is only relevant for
    the old code I did not want to change more then necessary to
    solve the concrete Problem.

    Fixes:
    kolab/issue4868

    CCBUG: 159296