Auth scheme state cache to use object serialization

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1600641 13f79535-47bb-0310-9956-ffa450edef68
Test case for HTTPCLIENT-1490

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1600737 13f79535-47bb-0310-9956-ffa450edef68