Fix review comment and test

Author: ashishkr200

hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/server/SCMClientProtocolServer.java

@@ -255,6 +255,13 @@ public ContainerWithPipeline allocateContainer(ReplicationConfig replicationConf
       getScm().checkAdminAccess(getRemoteUser(), false);
       final ContainerInfo container = scm.getContainerManager()
           .allocateContainer(replicationConfig, owner);
+      if (container == null) {
+        throw new SCMException(
+            "Could not allocate container for replication " + replicationConfig
+                + ", owner=" + owner
+                + ": no suitable open pipeline with enough space",
+            ResultCodes.FAILED_TO_ALLOCATE_CONTAINER);
+      }
       final Pipeline pipeline = scm.getPipelineManager()
           .getPipeline(container.getPipelineID());
       ContainerWithPipeline cp = new ContainerWithPipeline(container, pipeline);

hadoop-hdds/server-scm/src/test/java/org/apache/hadoop/hdds/scm/container/MockNodeManager.java

@@ -533,13 +533,6 @@ public int getPipelinesCount(DatanodeDetails datanodeDetails) {
   @Override
   public void addPipeline(Pipeline pipeline) {
     node2PipelineMap.addPipeline(pipeline);
-    // Pipeline creation uses DNs that may not be the pre-registered fake nodes; ensure each
-    // pipeline member has metrics so {@link #getDatanodeInfo} and space checks work.
-    for (DatanodeDetails dn : pipeline.getNodes()) {
-      if (nodeMetricMap.get(dn) == null) {
-        populateNodeMetric(dn, 0);
-      }
-    }
   }
 
   /**