The same checks to see if a drive can be or is registered are
repeated through the code, factor out the checks in a common function
and replace the repeated checks with it.
Signed-off-by: NHerton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>
Signed-off-by: NJens Axboe <axboe@kernel.dk>