NtWriteFile should check for granted access

Our current implementation just references the received FileObject without checking more into details what were the asked access and what are the granted ones.

This implementation is wrong and can lead to issues in case a read-only FSD is used and doesn't provide FastIO callback for write, a good example being MS CDFS.

We should instead be calling ObReferenceFileObjectForWrite() that performs this check.

(Source: http://fsfilters.blogspot.fr/2012/05/writing-to-read-only-files.html).

Once this bug is fixed, please remove hack committed in 5f25582