Fixes for CPP-928, and trusted certs

[maxdymond]

This PR consists of two commits:

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CPP-928 Ensure server name information flows through from contact point configuration

Previously during Address name resolution, the server name information for a given Address was lost. This fix ensures that the server name information flows through during the name resolution process for a given Address.

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Iterate over all certificates in a trusted cert BIO, not just the first

Previously the code which loaded a trusted certificate from file only assumed that there was a single certificate in that file, meaning that using a certificate bundle for certificate verification would not work.

This fix allows the driver to read multiple trusted certificates out of a BIO and provision them in the trusted certificate store.

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Please let me know if you have any comments!

[mpenick]

Hey, I think domain name verification is working as intended. The driver uses reverse DNS to lookup the name for certificate validation (which is a side effect of Cassandra using IP addresses internally). We have some SSL documentation that makes the use of those flags a bit clearer. I agree the header docs could do a better job of explaining those.

Cassandra uses IP addresses internally so those can be used directly for verification or a domain name can be used via reverse DNS (PTR record).

CassSsl* ssl = cass_ssl_new();

// CASS_SSL_VERIFY_PEER_IDENTITY_DNS (domain name)
cass_ssl_set_verify_flags(ssl, CASS_SSL_VERIFY_PEER_CERT | CASS_SSL_VERIFY_PEER_IDENTITY_DNS);

CassCluster* cluster = cass_cluster_new();

// Enable reverse DNS
cass_cluster_set_use_hostname_resolution(cluster, cass_true);

// ...

[kw217]

@mpenick @maxdymond Happy New Year! I've pulled out the uncontroversial part of this PR (the change to read all certs) into a separate PR; @mpenick please can you re-review and merge? It's just a cherry-pick, no code changes since you reviewed above. Thanks.