-was previously set to 30, which seems far too aggressive given that with
ActiveRegionWalkers, as with LocusWalkers, this limits the depth of any
pileup returned by LIBS
-250 is a more conservative default used by the UG
-can adjust down/up later based on further experiments (GSA-699 will
remain open)
-verified with Ryan that all integration test differences are either
innocent or represent an improvement
GSA-699