HTTPCLIENT-1348: Use plus character in addition to comma as a multi-value delimiter when extracting certificate CN in AbstractVerifier
Contributed by Vasil Badev <v_badev at infonotary.com>

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.2.x@1478930 13f79535-47bb-0310-9956-ffa450edef68