Set the candidate task windowing mode

A fullscreen task was unable to be started in to freefrom mode.
The behavior was broken after commit bbcd3435.

Bug: 229052728
Test: Start a recent task in freefrom
Test: atest ActivityStarterTests
Test: atest PinnedStackTests#testDisplayMetricsPinUnpin
Change-Id: I11bc49983a876da3f903dd2753fd8d2d447e2626