Destroy tiles created in tests

If tiles are not properly dispossed, their handlers may keep messages
past the test boundary.

Test: atest SystemUITests
Fixes 299491332

Change-Id: I100d246c30933d805dbe20e021e9e701953f97d3
(cherry picked from commit b95fa817d8c2b63685148d2974f4f6a4d37eb8da)
3 files changed