The "force_close" sysfs attribute remains to exist for some time
after q2t_close_session() finished. Avoid that q2t_close_session()
invokes q2t_sess_put() more than once by removing a session from
the session list before returning. Avoid that that disabling a
target after q2t_close_session() has been invoked triggers a call
of q2t_sess_put(). Avoid that triggering the "force_close" sysfs
attribute after a target has been disabled triggers an additional
call of q2t_sess_put().
git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4944 d57e44dd-8a1f-0410-8b47-8ef2f437770f