smbprovider: Add SMB1 unsupported ErrorType

Adds an error to the smbprovider::ErrorType enum to be used to
differentiate between a generic failure and a failure because a
specified share is SMB1 which we do not support.

BUG=chromium:757625
TEST=emerges
Change-Id: Ia2847f903d471c4015681a04303d2f01ce4310f1
Reviewed-on: https://chromium-review.googlesource.com/1195586


Commit-Ready: Zentaro Kavanagh <zentaro@chromium.org>
Tested-by: Zentaro Kavanagh <zentaro@chromium.org>
Tested-by: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>