cifs: Fix the target file was deleted when rename failed.

cifs: Fix the target file was deleted when rename failed.

When xfstest generic/035, we found the target file was deleted
if the rename return -EACESS.

In cifs_rename2, we unlink the positive target dentry if rename
failed with EACESS or EEXIST, even if the target dentry is positived
before rename. Then the existing file was deleted.

We should just delete the target file which created during the
rename.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>