[LOG4J2-320] JPAAppender stops logging because META-INF/log4j-provider.properties is left open. Refactor loading and closing a properties stream into a new method PropertiesUtil#loadClose().

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1511342 13f79535-47bb-0310-9956-ffa450edef68