Issue #199 - move reducer initializing to base class

ScaldingJobTask is a subclass of BaseHadoopJobTask and uses BHJT.jobconfs() to set up basic job parameters.  To allow for map-only jobs though, jobconfs() references self.reducer (which is only initialized in a separate BHJT subclass).  This moves self.reducer initialization from the subclass to the base class.

Change-Id: I54bc142b4f17789a7bc4c06e50b4a87b12149091