Consume MOVE from different devices one at a time

The events received by the spy window may be batched, and batches could
be processed out of order.
To avoid this confusing behaviour, consume the events one at a time.

Fixes: 332314982
Test: TEST=inputflinger_tests; m $TEST && adb sync && adb shell -t /data/nativetest64/$TEST/$TEST --gtest_filter="*MultiDevicePilfer" --gtest_repeat=10000 --gtest_break_on_failure
Change-Id: I9a50bea24401fa55b54687ab227bd2ed5c3d43ba