fix zombie process
fix zombie process

Trace Processor Python API can spawn zombie processes, see https://issuetracker.google.com/issues/238165693

Signed-off-by: Sui <1d08ce8d3d432bb5fbc0f61d0c59dfe576ee86f7@gmail.com>
Change-Id: I72cce1f7ed5fdd659040f9c542d6d9836ccb57a8

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto