In QMP, we want to use dashes instead of underscores in QMP argument
names, and use nested options for throttling.

The new option names affect the command line as well, but for
compatibility drive_init() will convert the old option names before
calling into the code that will be shared between -drive and
blockdev-add.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>