sheepdog: fix to clear create flag when reloading inode

This bug causes duplicated CREATE_AND_WRITE requests
in case of iSCSI multipath failover.

Signed-off-by: YAMADA Hideki <yamada.hideki@lab.ntt.co.jp>
Reviewed-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>