Revert "luci-base: support dnsmasq-filter-a (#167)"

[cuiyf5516]

This reverts commit afbe07de4ebf0b7f9f507dc947e8cf102266bf86.

Because of revert of "dnsmasq: bump to v2.87", revert this commit as well.

[aiamadeus]

Thanks, I will create a backport commit for dnsmasq to keep these in.