Revert "dnsmasq: Disable DNS server updation via STDIN on Brillo."

This reverts commit b265d6f2a9a7e2aad83bb0845aab56474d09a3cf. The
__BRILLO__ variable is obsolete.

Test: none
Change-Id: Ie9fe234d7dbdfe7e184590a1680f921c3cee81f3
3 files changed