Trivial Changes: Specify maven-assembly-plugin version to 2.8 for...

Trivial Changes: Specify maven-assembly-plugin version to 2.8 for release-client profile similar to release-all profile, reason of performing this change is that latest version of maven-assembly-plugin has removed finalName property.

pom.xml

@@ -461,6 +461,7 @@
                 <plugins>
                     <plugin>
                         <artifactId>maven-assembly-plugin</artifactId>
+                        <version>2.6</version>
                         <configuration>
                             <finalName>apache-rocketmq</finalName>
                             <descriptors>