Major Description
The SSLTestConfig constructor lets the call (notable SolrTestCaseJ4) tell it wether clientAuth should be used (note SolrTestCaseJ4 calls this boolean "trySslClientAuth") but it has a hardcoded assumption that the keystore file it can use (for both the keystore and the truststore) will exist at a fixed path in the solr install.
when this works, it works fine - but if end users subclass/reuse SolrTestCaseJ4 in their own projects, they may do so in a way that prevents the SSLTestConfig keystore assumptions from being true, and yet they won't get any sort of clear error.
