when running acme.sh headless (without terminal) to create a new key
createDomainKey returns a non-zero exit-code.
explicitly returning zero avoids this.
date -u -d@"12345" does not produce an error on *BSD and outputs the
current date in UTC, which is not the expected output from _time2str()
Fix, reorder _time2str() to attempt BSD style date first, which
errors on Linux, so cascade style OS detection works correctly.