set ABI to 2.slh.4.

* set ABI to 2.slh.4.
* add patches from the -stable queue:
  - target-iser-improve-cm-events-handling
  - target-iser-wait-for-proper-cleanup-before-unloading
  - target-iser-gracefully-reject-t10-pi-enabled-connect-request-if-not-
    supported
  - target-set-cmd_t_active-bit-for-task-management-requests
  - target-use-complete_all-for-se_cmd-t_transport_stop_comp
  - iscsi-target-fix-abort_task-connection-reset-iscsi_queue_req-memory-leak
  - target-iser-fix-a-wrong-dereference-in-case-discovery-session-is-over-
    iser
  - target-iscsi-fix-sendtargets-response-pdu-for-iser-transport
  - target-report-correct-response-length-for-some-commands
  - scsi_cmnd-introduce-scsi_transfer_length-helper
  - libiscsi-iser-adjust-data_length-to-include-protection-information
  - target-sbc-loopback-adjust-command-data-length-in-case-pi-exists-on-the-
    wire