PR: https://github.com/truenas/ports/pull/974

DOS attributes specified through SMB2 CREATE requests were not getting
set due to combination of parameters being used to enable kernel DOS
mode support and avoid extra xattr writes. This commit adds additional
handling for case where kernel DOS modes are supported and used by adding
new share-level parameter lp_kernel_dosmodes that is either manually set
or loaded at tcon by the VFS module. Additional check is made for kernel
DOS modes being enabled in code path for CREATE through SMB1/2 and the
relevant VFS operation called.