SOLR-5479: SolrCmdDistributor retry logic stops if a leader for the request cannot be found in 1 second.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_6@1553945 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5479: Deal with null message in SolrLogLayout

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_6@1553946 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5532: SolrJ Content-Type validation is too strict for some webcontainers / proxies.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_6@1553949 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5576: Improve concurrency when registering and waiting for all SolrCore's to register a DOWN state.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_6@1553954 13f79535-47bb-0310-9956-ffa450edef68