dnsmasq: get systemd only working again

The changes made in commit 2497cf29


[dnsmasq: steal resolvconf support from Ubuntu] broke systemd only
dnsmasq runtime. No sysvinit scripts are included in systemd only
builds (and should not be) and the dnsmasq executable has not moved to
/usr/sbin.

Reverting to the previous version of the systemd service file. If
folks want the local dnsmasq instance to be queried before going to
an external DNS they should add 'nameserver 127.0.0.1' to
/etc/resolv.conf. Or submit a change which will work with systemd.

Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
Acked-by: Anders Darander <anders@chargestorm.se>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>
(cherry picked from commit 237ade5065aee5290288febfbbae90145c2c7764)