Currently, ASYNC PDU default queue size is set to max connections.  This
leaves only one buffer per connection for any ASYNC PDUs from targets.

Double the size of the default queue.
Signed-off-by: NJitendra Bhivare <jitendra.bhivare@broadcom.com>
Reviewed-by: NTomas Henzl <thenzl@redhat.com>
Reviewed-by: NChris Leech <cleech@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>