Test scripts: change openssl default message digest from md5 to sha1 to make tests work on cent OS 7 where md5 is disabled by default, and setting OPENSSL_ENABLE_MD5_VERIFY=1 environment variable is required to enable it. It seems highly likely that the change to sha1 will not break tests on any other platforms, as sha1 is expected to be very likely compiled in by default with openssl 1.0.x.