[SCSI] lpfc 8.1.2: Fixed a double insertion of mail box object to the SLI mailbox list.

Fixed a double insertion of mail box object to the SLI mailbox list.

Signed-off-by: Jamie Wellnitz <Jamie.Wellnitz@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>