openfortivpn: add option to use ither curl or ping to test host status

allow use of curl rather than ping to test if a host
is up since a host may not respond to ping, but an
https request is part of the openfortivpn connection,
so this is a more reliable test

also clean up overly verbose logging

Signed-off-by: Aaron Goodman <aaronjg@stanford.edu>