Remove unresolved parent in cdh4-extras pom.xml

 * Remove the unresolved parent element in the pom.xml for thirdparty/cdh4-extras
 * Add configuration to specify source version because Maven 3 on Java 1.7 complains and assumes an older source version (1.3) for some reason. 

Tracked by the following JIRA: https://issues.cloudera.org/browse/IMPALA-982