[FLINK-8295] [cassandra] [build] Properly shade netty for the datasta…

…x driver

com.datastax.driver.core.NettyUtil expects netty to be present either at its
original package or relocated to com.datastax.shaded.netty. By relocating it
to this package we make sure the driver follows its designated path.

This closes apache#5183.

flink-connectors/flink-connector-cassandra/pom.xml

@@ -84,13 +84,13 @@ under the License.
  </excludes>
  </relocation>
  <!--
- For the details of relocation pattern, refer the discussion at
- https://github.com/apache/flink/pull/4545
- FLINK-6805
+ Relocate to datastax' package where it
+ expects shaded netty versions; see
+ https://issues.apache.org/jira/browse/FLINK-8295
  -->
  <relocation>
  <pattern>io.netty</pattern>
- <shadedPattern>org.apache.flink.cassandra.shaded.io.netty</shadedPattern>
+ <shadedPattern>com.datastax.shaded.netty</shadedPattern>
  </relocation>
  </relocations>
  </configuration>