[GCPW] Disallow sign in of consumer accounts when mdm is enabled.

Unless the registry key "mdm_aca" is explicitly set to 1, always
fail sign in of consumer accounts when mdm enrollment is enabled.

Consumer accounts are defined as accounts with gmail.com or
googlemail.com domain.

Bug: 944049
Change-Id: Icb822f3737d90931de16a8d3317616dd2b159edd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1532903
Commit-Queue: Tien Mai <tienmai@chromium.org>
Reviewed-by: Roger Tawa <rogerta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#646278}
HRESULT CGaiaCredentialBase::SetComboBoxSelectedValue(DWORD field_id,
                                                      DWORD dwSelectedItem) {
  return E_NOTIMPL;
}

HRESULT CGaiaCredentialBase::SetComboBoxSelectedValue(DWORD field_id,
                                                      DWORD dwSelectedItem) {
  return E_NOTIMPL;
}
