tests: Fall back on host/getent in ts_resolve_host

tests: Fall back on host/getent in ts_resolve_host

Neither dig or nslookup would be my first option for resolving,
so add the host utility of ISC/bind fame and the (slow) getent
utility shipped with libc.

This extends the conditions introduced in ...

  commit a98de9696e1a898f925c9154e5693e73aec0779d
  Author: Ruediger Meier <ruediger.meier@ga-group.nl>
  Date:   Wed Jun 11 19:28:20 2014 +0200

      tests: skip some last tests if no dns support

... and should help us not skip certain tests when we have
network connection but none of dig or nslookup available.

Signed-off-by: Andreas Henriksson <andreas@fatal.se>