Revert "AP_NavEKF : Reduce ripple in estimates that can cause copter motor 'pulsing'"

This reverts commit 13df6fb1c9.

This patch was a result of an incorrect merge of the optflow branch
into master. It reintroduced the bug fixed by this commit:

  AP_NavEKF : Fix bug in reset of GPS glitch offset
  8aa267f75f

libraries/AP_NavEKF/AP_NavEKF.cpp

@@ -486,8 +486,6 @@ void NavEKF::ResetPosition(void)
         storedStates[i].position[0] = state.position[0];
         storedStates[i].position[1] = state.position[1];
     }
-    // reset the glitch ofset correction states
-    gpsPosGlitchOffsetNE.zero();
 }
 
 // resets velocity states to last GPS measurement or to zero if in static mode