Kill IndexReaderFactoryTest: the only thing it asserts is a lie.  Move that (fixed) assertion to AlternateDirectoryTest where it's already true. (merge r1511142)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1511143 13f79535-47bb-0310-9956-ffa450edef68