Set up JDK 11 for SonarCloud in github action. (#3052)

* Set up JDK 11 for SonarCloud in github action.

* Fix javadoc error with JDK 11.

* Prevent Javadoc from stopping if it finds any html errors.

.github/workflows/ci_ut.yml

@@ -67,10 +67,14 @@ jobs:
       - name: Upload coverage report to codecov
         run: |
           CODECOV_TOKEN="09c2663f-b091-4258-8a47-c981827eb29a" bash <(curl -s https://codecov.io/bash)
+      # Set up JDK 11 for SonarCloud.
+      - name: Set up JDK 1.11
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.11
       - name: Run SonarCloud Analysis
         run: >
-          mvn verify --batch-mode
+          mvn --batch-mode verify sonar:sonar
-          org.sonarsource.scanner.maven:sonar-maven-plugin:3.6.1.1688:sonar
           -Dsonar.coverage.jacoco.xmlReportPaths=target/site/jacoco/jacoco.xml
           -Dmaven.test.skip=true
           -Dsonar.host.url=https://sonarcloud.io

pom.xml

@@ -597,6 +597,10 @@
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-javadoc-plugin</artifactId>
                     <version>${maven-javadoc-plugin.version}</version>
+                    <configuration>
+                        <source>8</source>
+                        <failOnError>false</failOnError>
+                    </configuration>
                 </plugin>
 
                 <plugin>