getPeerCertificateChain() to throw exception when client auth not requested

[JeremiahM37]

Summary

Fix getPeerCertificateChain() to throw SSLPeerUnverifiedException when client auth not requested, matching SunJSSE behavior.

Problem

SSLSession.getPeerCertificateChain() returned null when the server didn't request client authentication. SunJSSE throws SSLPeerUnverifiedException in this case. This caused compatibility issues with Netty and other frameworks that catch the exception to detect "no peer certificate."

Changes

• WolfSSLImplementSSLSession.java: Throw SSLPeerUnverifiedException instead of returning null when client auth not requested

Testing

• Added testGetPeerCertificateChainNoClientAuth to verify exception is thrown when needClientAuth=false and wantClientAuth=false