camcontrol: Force a rescan of the lun after firmware download.

After downloading the firmware to a device, it's inquiry data likely
will change. Force a rescan of the target with the CAM_EXPECT_INQ_CHANGE
flag to get it to record the new inqury data as being expected. This
avoids the need for a 'camcontrol rescan' on the device which detaches
and re-attaches the disk (da, ada) device. This brings fwdownload up to
nvmecontrol's ability to do the same thing w/o changing the exposed
nvme/nvd/nda device. We scan the target and not the LUN because dual
actuator drives have multiple LUNs, but the firmware is global across
many vendors' drives (and the so far theoretical ones that aren't won't
be harmed by the rescan).

Since the underlying struct disk is now preserved accross this
operation, it's now possible to upgrade firmware of a root device w/o
crashing the system. On systems that are quite busy, the worst that
happens is that certain operaions are reported cancelled when the new
firmware is activated. These operations are retried with the normal CAM
recovery mechanisms and will work on the retry. The only visible hiccup
is the time that new firmware is flashing / initializing. One should not
consider this operation completely risk free, however, since not all
drives are well behaved after a firmware download.

MFC After: 1 week
Relnotes: yes
Sponsored by: Netflix
Feedback by: mav
Differential Revision: https://reviews.freebsd.org/D34325