Fixing CI

There's an issue with the downstream PPA "ondrej/php" where is cannot find the gearman
package.

Refactoring Dockerfile to use standard base images as a workaround

Author: JimTools

Tests/RdKafkaConsumerTest.php

@@ -190,6 +190,7 @@ public function testShouldReceiveFromQueueAndReturnMessageIfMessageInQueue()
         $kafkaMessage = new Message();
         $kafkaMessage->err = \RD_KAFKA_RESP_ERR_NO_ERROR;
         $kafkaMessage->payload = 'theSerializedMessage';
+        $kafkaMessage->partition = 0;
 
         $kafkaConsumer = $this->createKafkaConsumerMock();
         $kafkaConsumer