Bump 6.6 branch to version 6.6.1 (#37975)

Author: matriv

buildSrc/version.properties

@@ -1,4 +1,4 @@
-elasticsearch     = 6.6.0
+elasticsearch     = 6.6.1
 lucene            = 7.6.0
 
 # optional dependencies

server/src/main/java/org/elasticsearch/Version.java

@@ -198,12 +198,12 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_6_5_3 = new Version(V_6_5_3_ID, org.apache.lucene.util.Version.LUCENE_7_5_0);
     public static final int V_6_5_4_ID = 6050499;
     public static final Version V_6_5_4 = new Version(V_6_5_4_ID, org.apache.lucene.util.Version.LUCENE_7_5_0);
-    public static final int V_6_5_5_ID = 6050599;
-    public static final Version V_6_5_5 = new Version(V_6_5_5_ID, org.apache.lucene.util.Version.LUCENE_7_5_0);
     public static final int V_6_6_0_ID = 6060099;
     public static final Version V_6_6_0 = new Version(V_6_6_0_ID, org.apache.lucene.util.Version.LUCENE_7_6_0);
+    public static final int V_6_6_1_ID = 6060199;
+    public static final Version V_6_6_1 = new Version(V_6_6_1_ID, org.apache.lucene.util.Version.LUCENE_7_6_0);
 
-    public static final Version CURRENT = V_6_6_0;
+    public static final Version CURRENT = V_6_6_1;
 
     static {
         assert CURRENT.luceneVersion.equals(org.apache.lucene.util.Version.LATEST) : "Version must be upgraded to ["
@@ -216,10 +216,10 @@ public static Version readVersion(StreamInput in) throws IOException {
 
     public static Version fromId(int id) {
         switch (id) {
+            case V_6_6_1_ID:
+                return V_6_6_1;
             case V_6_6_0_ID:
                 return V_6_6_0;
-            case V_6_5_5_ID:
-                return V_6_5_5;    
             case V_6_5_4_ID:
                 return V_6_5_4;
             case V_6_5_3_ID:

x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/action/TransportOpenJobActionTests.java

@@ -441,8 +441,9 @@ public void testSelectLeastLoadedMlNode_indexJobsCannotBeAssignedToPre660Node()
         Job job = jobWithRules("v660-job");
         Assignment result = TransportOpenJobAction.selectLeastLoadedMlNode("v660-job", job, cs.build(), 2, 10, 30, memoryTracker, logger);
         assertNull(result.getExecutorNode());
-        assertEquals("Not opening job [v660-job] on node [_node_name1] version [6.5.0], " +
-                "because this node does not support jobs of version [6.6.0]", result.getExplanation());
+        assertThat(result.getExplanation(),
+            containsString("Not opening job [v660-job] on node [_node_name1] version [6.5.0], " +
+                "because this node does not support jobs of version [6.6."));
 
         nodes = DiscoveryNodes.builder()
                 .add(new DiscoveryNode("_node_name1", "_node_id1", new TransportAddress(InetAddress.getLoopbackAddress(), 9300),