sheepdog: Fix blockdev-add

sheepdog: Fix blockdev-add

Commit 831acdc "sheepdog: Implement bdrv_parse_filename()" and commit
d282f34 "sheepdog: Support blockdev-add" have different ideas on how
the QemuOpts parameters for the server address are named.  Fix that.
While there, rename BlockdevOptionsSheepdog member addr to server, for
consistency with BlockdevOptionsSsh, BlockdevOptionsGluster,
BlockdevOptionsNbd.

Commit 831acdc's example becomes

    --drive driver=sheepdog,server.type=inet,server.host=fido,server.port=7000,vdi=dolly

instead of

    --drive driver=sheepdog,host=fido,vdi=dolly

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Kashyap Chamarthy <kchamart@redhat.com>
Message-id: 1490895797-29094-10-git-send-email-armbru@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>