Use systemd-resolve to check if resolved is running

Use systemd-resolve to check if resolved is running

resolved may be included in nsswitch.conf even though systemd-resolved
is not running. E.g. Arch Linux includes resolved in nsswitch.conf by
default, but systemd-resolved is not enabled by default, which causes
this script to fail updating dns.

This patch uses the systemd-resolve command, which is included with
systemd, to check if systemd-resolved is actually running.

Signed-off-by: Trygve Aaberge <trygveaa@gmail.com>
Signed-off-by: Daniel Lenski <dlenski@gmail.com>