r3830: unified the query/set security descriptor code with the rest of the

r3830: unified the query/set security descriptor code with the rest of the
queryfileinfo/setfileinfo logic, so querying/setting a security
descriptor is treated as just another file query/set operation.

This will allow NTVFS backends to see the query/set security
descriptor operations as RAW_FILEINFO_SEC_DESC and
RAW_SFILEINFO_SEC_DESC operations.