Update git submodules
Update git submodules

* Update plugins/replication from branch 'stable-2.16'
  to 18857e12579d841693c2dc39e9ee330ab36bca65
  - Fix NPE when username or password isn't specified for remote
    
    When the username or password is not specified, pass an empty
    string instead of null.
    
    Change-Id: I49121b9873eb9f2800417b6d264cc2ad82047f85
    
WANdisco/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,WANdisco/gerrit,WANdisco/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit