[SCSI] ibmvfc: Fix another hang on module removal

This fixes a hang on module removal. The module removal code was setting
the hosts's state to IBMVFC_HOST_OFFLINE before tearing down the kernel
thread, but, due to a bug in ibmvfc_wait_while_resetting, was not waiting
for the kernel thread's offlining work to be done prior to destroying
the kernel thread, which left the scsi host in a blocked state which we
never got out of.

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