libiscsi: check reason why we are stopping iscsi session to determine error value

Some wires got crossed on some patches and I messed up in the code
below when rebuilding a patch. We want to be checking if flag
equaled the value indicating if we killing the session due to
final logout or if we just trying to relogin.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>