Specify push configurations for gerrit's replication in lists

The multiline push statements got rendered to

  push =   push = +refs/tags/*:refs/tags/*
  push = +refs/heads/*:refs/heads/*

in replication.config. While refs/heads/* did get replicated,
refs/tags/* did not. We now specify the different push configurations
in lists; similar to the urls for 'jenkins-salves'.

Bug: 53597
Change-Id: I26715cc8972be1fff6c0c7e77270ac9f265eaa79