APPLIED: [Xenial][PULL] CIFS: Enable encryption for SMB3

[Thadeu Lima de Souza Cascardo]

I have applied this to xenial master-next branch.

However, we would like to have seen this tested with the 4.4 kernel, and
a build was given in the bug for the last rebase. We are going to watch
for any problems on CIFS during the next weeks.

Thanks.
Cascardo.