[FLINK-10922] Exclude transitive kafka-clients dependency from base flink-connector-kafka

In order to satisfy dependency convergence we need to exclude the kafka-clients from the base
flink-connector-kafka-x dependency in every flink-connector-kafka-y module.

This closes apache#7140.

Author: tillrohrmann

flink-connectors/flink-connector-kafka-0.10/pom.xml

@@ -53,6 +53,10 @@ under the License.
 					<groupId>org.apache.kafka</groupId>
 					<artifactId>kafka_${scala.binary.version}</artifactId>
 				</exclusion>
+				<exclusion>
+					<groupId>org.apache.kafka</groupId>
+					<artifactId>kafka-clients</artifactId>
+				</exclusion>
 			</exclusions>
 		</dependency>
 

flink-connectors/flink-connector-kafka-0.11/pom.xml

@@ -53,6 +53,10 @@ under the License.
 					<groupId>org.apache.kafka</groupId>
 					<artifactId>kafka_${scala.binary.version}</artifactId>
 				</exclusion>
+				<exclusion>
+					<groupId>org.apache.kafka</groupId>
+					<artifactId>kafka-clients</artifactId>
+				</exclusion>
 			</exclusions>
 		</dependency>
 

flink-connectors/flink-connector-kafka-0.9/pom.xml

@@ -60,6 +60,10 @@ under the License.
 					<groupId>org.apache.kafka</groupId>
 					<artifactId>kafka_${scala.binary.version}</artifactId>
 				</exclusion>
+				<exclusion>
+					<groupId>org.apache.kafka</groupId>
+					<artifactId>kafka-clients</artifactId>
+				</exclusion>
 			</exclusions>
 		</dependency>