mount: ignore subvol argument in btrfs sb
mount: ignore subvol argument in btrfs sb

See comment for details, but basically this mountopt can be completely
wrong in some cases.

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@virtuozzo.com>

KKoukiou/criu-remote,AuthenticEshkinKot/criu,efiop/criu,KKoukiou/criu-remote,AuthenticEshkinKot/criu,efiop/criu,efiop/criu,AuthenticEshkinKot/criu,AuthenticEshkinKot/criu,efiop/criu,AuthenticEshkinKot/criu,KKoukiou/criu-remote,eabatalov/criu,KKoukiou/criu-remote,efiop/criu,eabatalov/criu,eabatalov/criu,KKoukiou/criu-remote,KKoukiou/criu-remote,eabatalov/criu,AuthenticEshkinKot/criu,efiop/criu,eabatalov/criu,eabatalov/criu