When reporting some major UNIT ATTENTION condition, like POWER ON OCCURRED
or I_T NEXUS LOSS, clear all minor UAs for the LUN, redundant in this case.

All SAM specifications tell that target MAY do it, but libiscsi initiator
seems require it to be done, terminating connection with error if some more
UAs happen to be reported during iSCSI connection.

MFC after:	3 days

(cherry picked from commit 1a79276d79d92d41c2be872b5393c48ceb832143)