lookup_hostname("localhost") occassionally timed out (after allowed 10
secs) when running test suite on some systems. Not sure why, but
changed to use the Exec module for when block conditions instead as the
scope of the test doesn't depend on a particular type of condition, it
just needs something that will work reliably/quickly.
May fix a sporadic failure, in which case it was just not getting enough
time to run or lookup_hostname() taking longer than ~3 seconds. Else,
the new output should give more hints on what's going wrong. In any
case, termination conditions for the test are now explicit.
