Observed on VS 2015 variants in patch builds (one, two).

Given the C driver CA certificate being registered on the system and a mock KMS server running on port 7999, the TLS handshake as initiated by test_kms_tls_cert_valid() fails with the error SSL Certification verification failed: hostname doesn't match certificate when attempting to resolve "127.0.0.1:7999", but succeeds when "localhost:7999" is provided instead. This suggests there may be a bug in the Secure Channel library's implementation of hostname resolution in the version being used by the VS 2015 variant on Evergreen.