[SCSI] ibmvfc: Reduce error logging noise

The ibmvfc driver currently logs errors during discovery for several
transient fabric errors, which generally get retried. If retries
do not work, we see multiple errors in the log. If retries do work,
we see errors in the log which may be confusing since the retry worked.
This patch enhances the discovery time error logging to only log errors
for command failures during discovery if all allowed retries have been
used up. The existing behavior of logging all failures can be restored
by setting the hosts log_level to a value of 3 or greater.

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