Fix "null cert chain" error when trying to secure s2s connection
When remote servers are using self-signed certificates or certificates with no certificate chain then Wildfire will just fail with a "null cert chain" error. Therefore, TLS will not succeed. Instead, if Wildfire is configured to not validate certificates, accept signed certificates or not validate certificate chains then we must indicate the SSLEngine that we just want (and not need) client authentication. Making this modification will instruct Java to accept certificates with no chain.