nvme-fcloop: fix deallocation of working context

There's been a longstanding bug of LS completions which freed ls ops,
particularly the disconnect LS, while executing on a work context that
is in the memory being free. Not a good thing to do.

Rework LS handling to make callbacks in the rport context rather than
the ls_request context.

Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>