cifs: set oparms.create_options rather than or'ing in CREATE_OPEN_BACKUP_INTENT

Currently oparms.create_options is uninitialized and the code is logically
or'ing in CREATE_OPEN_BACKUP_INTENT onto a garbage value of
oparms.create_options from the stack.  Fix this by just setting the value
rather than or'ing in the setting.

Detected by CoverityScan, CID#1447220 ("Unitialized scale value")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>