[SCSI] ibmvscsi: Abort path fix

Since it is completely possible for scsi core to call
a LLDD's eh_abort function after the command has completed,
fix ibmvscsi to return SUCCESS if this is the case.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>