Setting version to 2.0.4-SNAPSHOT in branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1442956 13f79535-47bb-0310-9956-ffa450edef68
Preparing for hadoop-2.0.3-alpha release.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1442960 13f79535-47bb-0310-9956-ffa450edef68