Just make the forkCount to 0 in sure fire plugin configurations

<plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>2.22.2</version>
       <configuration>
          <suiteXmlFiles>
              <suiteXmlFile>testng_jenkins.xml</suiteXmlFile>
           </suiteXmlFiles>
       <forkCount>0</forkCount>
      </configuration>
</plugin>