The noop check m_sortRole == role has to be removed
because the hash table m_roleIds can change between two calls to
setSortRole (as it actually happens when resync the hash table).
Possibly one could perform a more clever check (i.e. adding some
m_invalidated flag which would override the check), but I am not sure it is
really worth it.
This fixes sorting issues in the Plasma Device Notifier
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