Avoid un-necessarily recreating DBG_VALUEs on call instructions.
In LiveDebugValues, we choose to ignore any clobbers of the stack pointer by call instructions, because they're irrelevant to our model of the machine. Otherwise, SP based locations could be terminated un-necessarily. In InstrRefBasedLDV::transferRegisterDef, we correctly ignore such clobbers when updating what values are in which registers (MTracker), but we tell the block variable location tracker (TTracker) that the stack pointer has been clobbered. This caused the modified test to fail as an un-necessary DBG_VALUE was created.
This patch just corrects what we're already trying to do: as well as ignoring stack-pointer clobbers by calls for register tracking, also ignore them for variable location tracking, and don't report the clobber to TTracker.