Merge pull request apache#342 from tgravescs/fix_maven_protobuf

Change protobuf version for yarn alpha back to 2.4.1

The maven build for yarn-alpha uses the wrong protobuf version and hence the generated assembly jar doesn't work with Hadoop 0.23.  Removing the setting for the yarn-alpha profile since the default protobuf version is 2.4.1 at the top of the pom file.

pom.xml

@@ -727,7 +727,6 @@
         <hadoop.major.version>2</hadoop.major.version>
         <!-- 0.23.* is same as 2.0.* - except hardened to run production jobs -->
         <hadoop.version>0.23.7</hadoop.version>
-        <protobuf.version>2.5.0</protobuf.version>
         <!--<hadoop.version>2.0.5-alpha</hadoop.version> -->
       </properties>