SOLR-5517: Return HTTP error on POST requests with no Content-Type

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1547467 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5354: applying hoss's patch to fix function edge case in distributed sort (merged trunk r1547430)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1547473 13f79535-47bb-0310-9956-ffa450edef68