os/bluestore: make 'bluestore_debug_enforce_settings' control

os/bluestore: make 'bluestore_debug_enforce_settings' control
rotational/non-rotational OSD behavior for DB/WAL devices.

Prior to this commit this parameter determined what device class
settings to apply for BlueStore only. OSD had partially applied
actual journal/db/main device class for some operations, e.g. benchmark
on init or allocmap persistence, irrespective to this setting value.
This commit allows 'bluestore_debug_enforce_settings" to override the
actual device class completely.

Signed-off-by: Igor Fedotov <igor.fedotov@croit.io>