[test suite] check for fwknopd ready to receive packets

This commit was inspired through conversations with George Herlin.
[test suite] added tests/python_fko.pl for python tests
fixed two type mismatch compilation warnings for the perl FKO extension
[test suite] Reorganize client/server interactions to be more rigorous

This is a significant commit that alters how the test suite interacts with the
fwknop client and server by looking for indications that SPA packets are
actually received.  This is done by first waiting for 'main event loop' in
fwknopd log output to ensure that fwknopd is ready to receive packets, sending
the SPA packet(s), and then watching for for 'SPA Packet from IP' in fwknopd
output.  This is an improvement over the previous strategy that was only based
on timeout values since it works identically regardless of whether fwknop is
being run under valgrind or when the test suite is run on an embedded system
with very limited resources.  Another check is run for fwknopd receiving the
SIGTERM signal to shutdown via 'fwknopd -K', and that failing, the test suite
manually kills the process (though this should be rarely needed).

The above strategy is the result of discussions with George Herlin who proposed
the verification-based approach to test suite operations.

Other things this commit changes is the ability to detect whether OpenSSL
supports the 'hexkey:<key>' style specification for HMAC keys (an older version
of FreeBSD doesn't support this) and falls back to the '-hmac <key>' method if
not.