Detect unsupported PREVENT ALLOW MEDIUM REMOVAL and SYNCHRONIZE CACHE(10)
to not spam devices with useless commands and logs with errors.

(cherry picked from commit 3be5fcbcfd0d79067617f4be3e084cf64188a218)
Oops, revert unwanted part of r253721.

(cherry picked from commit 1e4488ade806c781c177abec051ee54bfc5143a6)
Improve r253721 by reporting detected lack of BIO_FLUSH support to GEOM.
That prevents more of such requests from coming and errors from logging.

(cherry picked from commit 329753c36e1e9d64afce0bc82c9a4f02a64b7934)