Support general systemd-resolve interface
Some Linux based OS use systemd-resolve service that is not based on nss-resolve or does not contain 'resolve' option on the /etc/nsswitch.conf
This patch add support for CISCO_SPLIT_DNS, CISCO_DEF_DOMAIN and INTERNAL_IP4_DNS via general systemd-resolve interface
Signed-off-by: Oleg Kofman oleg.kofman@gmail.com