[zanata/zanata-platform] 39ca8c: Use SLF4J MDC, not Log4j

[GitHub]

  Branch: refs/heads/slf4j-mdc
  Home:   https://github.com/zanata/zanata-platform
  Commit: 39ca8cee69e1544590e92d9d5d004d080a2209b9
      https://github.com/zanata/zanata-platform/commit/39ca8cee69e1544590e92d9d5d004d080a2209b9
  Author: Sean Flanigan <sflaniga at redhat.com>
  Date:   2017-08-21 (Mon, 21 Aug 2017)

  Changed paths:
    M server/services/src/main/java/org/zanata/security/UsernameLoggingFilter.java

  Log Message:
  -----------
  Use SLF4J MDC, not Log4j