7175133: jinfo failed to get system properties after 6924259 Summary: String offset and count fields as fix of 6924259 were removed, and become optional. SA still use offset and count fields to read String contents and failed. Fix if they exist, use them other then use value field only to read, this keeps consistent with the changes in 6924259. Reviewed-by: dholmes, mikael Contributed-by: yumin.qi@oracle.com

project=jdk8