LUCENE-5303: clear cache before each test

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1535215 13f79535-47bb-0310-9956-ffa450edef68

lucene/facet/src/java/org/apache/lucene/facet/search/OrdinalsCache.java

@@ -141,4 +141,9 @@ public class OrdinalsCache {
     }
     return size;
   }
+
+  /** Clears all entries from the cache. */
+  public synchronized static void clear() {
+    ordsCache.clear();
+  }
 }

lucene/facet/src/test/org/apache/lucene/facet/search/OrdinalsCacheTest.java

@@ -73,6 +73,8 @@ public class OrdinalsCacheTest extends FacetTestCase {
       };
     }
 
+    OrdinalsCache.clear();
+
     long ramBytesUsed = 0;
     for (Thread t : threads) {
       t.start();