Don't return a broken configuration in case of parse error.

  - Related to LOG4J2-619.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1602778 13f79535-47bb-0310-9956-ffa450edef68
Make the plugin building process debug log messages more useful again.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1602779 13f79535-47bb-0310-9956-ffa450edef68
Make another log message more clear.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1602780 13f79535-47bb-0310-9956-ffa450edef68