MFV r318962: Allow PROBE_SPINUP to fail in CAM ATA transport

MFV r318962: Allow PROBE_SPINUP to fail in CAM ATA transport

The motivation for this is two-fold.

1. Some old WD SATA disks may appear as if they need to be spun up
when they are already spinning.  Those disks would respond with
an error to the spin-up request.

2. Even if we really fail to spin up the disk, we still can try to
proceed to the subsequent phases.  If we fail later on, then no
difference.  Otherwise we get a chance to communicate with the
disk which is better than completely ignoring it, because a user
can try to recover the disk.

git-svn-id: svn://svn.freebsd.org/base/stable/10@323737 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f