[HUDI-2080] Move to ubuntu-18.04 for Azure CI (#3409)

Update Azure CI ubuntu from 16.04 to 18.04 due to 16.04 will be removed soon

Fixed some consistently failed tests

* fix TestCOWDataSourceStorage TestMORDataSourceStorage
* reset mocks

Also update readme badge



Co-authored-by: Raymond Xu <2701446+xushiyan@users.noreply.github.com>

hudi-client/hudi-client-common/src/test/java/org/apache/hudi/callback/http/TestCallbackHttpClient.java

@@ -18,14 +18,16 @@
 
 package org.apache.hudi.callback.http;
 
+import org.apache.hudi.callback.client.http.HoodieWriteCommitHttpCallbackClient;
+
 import org.apache.http.StatusLine;
 import org.apache.http.client.methods.CloseableHttpResponse;
 import org.apache.http.impl.client.CloseableHttpClient;
-import org.apache.hudi.callback.client.http.HoodieWriteCommitHttpCallbackClient;
 import org.apache.log4j.AppenderSkeleton;
 import org.apache.log4j.Level;
 import org.apache.log4j.Logger;
 import org.apache.log4j.spi.LoggingEvent;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.ArgumentCaptor;
@@ -39,6 +41,7 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -63,6 +66,11 @@ public class TestCallbackHttpClient {
   @Mock
   StatusLine statusLine;
 
+  @AfterEach
+  void resetMocks() {
+    reset(appender, httpClient, httpResponse, statusLine);
+  }
+
   private void mockResponse(int statusCode) {
     when(statusLine.getStatusCode()).thenReturn(statusCode);
     when(httpResponse.getStatusLine()).thenReturn(statusLine);

hudi-client/hudi-client-common/src/test/java/org/apache/hudi/metrics/datadog/TestDatadogHttpClient.java

@@ -27,6 +27,7 @@ import org.apache.log4j.AppenderSkeleton;
 import org.apache.log4j.Level;
 import org.apache.log4j.Logger;
 import org.apache.log4j.spi.LoggingEvent;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -46,6 +47,7 @@ import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -67,6 +69,11 @@ public class TestDatadogHttpClient {
   @Mock
   StatusLine statusLine;
 
+  @AfterEach
+  void resetMocks() {
+    reset(appender, httpClient, httpResponse, statusLine);
+  }
+
   private void mockResponse(int statusCode) {
     when(statusLine.getStatusCode()).thenReturn(statusCode);
     when(httpResponse.getStatusLine()).thenReturn(statusLine);

hudi-client/hudi-client-common/src/test/java/org/apache/hudi/metrics/datadog/TestDatadogReporter.java

@@ -28,6 +28,7 @@ import org.apache.log4j.AppenderSkeleton;
 import org.apache.log4j.Level;
 import org.apache.log4j.Logger;
 import org.apache.log4j.spi.LoggingEvent;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.ArgumentCaptor;
@@ -41,6 +42,7 @@ import java.util.concurrent.TimeUnit;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.verify;
 
 @ExtendWith(MockitoExtension.class)
@@ -58,6 +60,11 @@ public class TestDatadogReporter {
   @Mock
   DatadogHttpClient client;
 
+  @AfterEach
+  void resetMocks() {
+    reset(appender, registry, client);
+  }
+
   @Test
   public void stopShouldCloseEnclosedClient() throws IOException {
     new DatadogReporter(registry, client, "foo", Option.empty(), Option.empty(),