Motivation:
PR #5493 added support for KeyManagerFactories when using the OpenSsl context. This commit corrects a bug causing a NullPointerException that occurs when using a KeyManagerFactory without a certificate chain and private key.
Modifications:
Removes assertNotNull() assertions which were causing a certificate chain and private key to be required even when using a KeyManagerFactory. Also removed a redundant call to buildKeyManagerFactory() which was also causing a exception when a KeyManagerFactory is provided but a certificate chain and private key is not.
Result:
A KeyManagerFactory can now be used in the OpenSslServerContext without an independent certificate chain and private key.