Call setOverviewDragState() whenever taskbar is recreated

* Un/Pinning taskbar re-creates controllers which led to
stale state for checking if we are allowing split selection

Test: Crash/immediately going into split no longer repros after
un/pinning taskbar in overview and trying to split
Fixes: 326356246

Change-Id: I06cfc4d1c3c7fe071f04414c3134eaff7960ade6
(cherry picked from commit 0adca267)