improve handling of an empty dnsmasq --domain

Currently all domains passed through the dnsmasq --domain option,
are single quoted.  It's not fully understood how dnsmasq handles
single quotes in this situation, so it's safer to just avoid the
--domain option in this case.

Fixes bug: 1161506
Fixes bug: 1167447
Change-Id: I8ecd996676189f53908abd48fee81132091ee820
Cherry-picked: 24b9731af34fbc2fb17c849cb8cdb5c7a10db77d