Increase HandlerUtilsTest timeout to 500ms

The test is currently 1~3% flaky with a 200ms timeout, in particular it
may fail if a GC runs while waitForIdle is running.

Increase the timeout to 1s, which should be enough to cover such cases.

Change-Id: Ic6d4ff18fb81feb09639442196cdef3c5cfdf30c
Fixes: 302949876
Test: TH