[test suite] added --enable-openssl-checks

[test suite] added --enable-openssl-checks

Added --enable-openssl-checks to send all SPA packets encrypted via libfko
through the OpenSSL library to ensure that the libfko usage of AES is always
compatible with OpenSSL.  This ensures that the fwknop usage of AES is properly
implemented as verified by the OpenSSL library, which is a frequently audited
high profile crypto engine.  If a vulnerability is discovered in OpenSSL and a
change is made, then the --enable-openssl-checks mode will allow the test suite
to discover this in a automated fashion for fwknop.