Revert "Make VPA.setInterpolator(null) unset the interpolator."
Revert "Make VPA.setInterpolator(null) unset the interpolator."

This reverts commit 8cebf3a098eeff1f4b2359c4a3abdaf0e4dc494f.

Bug: 21804709
Change-Id: I4b3c2c4721b8e7dd5cb38c806bdd078344b09799

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base