SOLR-5285: use FieldType methods to be less brittle

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1601044 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6148: Trying to fix Jenkins failures by not LazyLoading the ParallelExecutor in CoreAdminHandler

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1601047 13f79535-47bb-0310-9956-ffa450edef68