Currently, QEMU chooses a drive type automatically based on the inserted
media. If there is no disk inserted, it chooses a 1.44MB drive type.

Change this behavior to be configurable, but leave it defaulted to 1.44.

This is not earnestly intended to be used by a user or a management
library, but rather exists so that pre-2.6 board types can configure it
to be a legacy value.
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Message-id: 1453495865-9649-8-git-send-email-jsnow@redhat.com