Inline calls to EvalAndHashBuild/Probe.

In the expr refactoring branch, AggregationNode::CodegenProcessRowBatch()
was failing to replace the calls to EvalBuild/ProbeRow() (which are
called in EvalAndHashBuild/Probe). We can avoid this via inlining.

Change-Id: I4f0bc65e390baf8c2b88fc7997062b83c8f9c7ec
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3787
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins