ValidateCertificate should be able to validate certificate chain

[asbachb]

I guess zend should be able to verify the certification chain like every other ssl enabled service (httpd, imaps, ...)

Adding the intermediate certificate like described in step 3,4 (https://zencash.atlassian.net/wiki/spaces/ZEN/pages/7537014/Part+6+-+Procure+and+Configure+Certificate) should not be necessary if ValidateCertificate (https://github.com/ZencashOfficial/zen/blob/48bba6a7b46f428b75f4cd925ff91d1f1fd462b2/src/zen/utiltls.cpp#L417) would behave correctly.

A problem which might help with that issue is that zend is currently not providing the entire certificate chain during handshake.
see https://github.com/asbachb/zen/blob/master/src/zen/tlsmanager.cpp#L183

[tarrenj]

Also see #85 and #85