[SCSI] lpfc 8.3.15: BSG, Discovery, and Misc fixes

- BSG interface related:
  - Fix node reference count if node is active
  - Warn if we're overwriting an active CT context

- Discovery related:
  - Clear "Ignore Reg Login" flag when purging mailbox queue
  - Pay attention to return code for fc_block_scsi_eh()
  - Stall device loss code if we're almost done when it fires
    (we're logged in, but PRLI is outstanding)

- Bugs
  - Correct DIF code for endianness issues
  - Correct where we had missed points to check txq on i/o
    completion/cleanup

Signed-off-by: Alex Iannicelli <alex.iannicelli@emulex.com>
Signed-off-by: James Smart <james.smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>