Ignore issue #16671 test on android

Seems to be blocking forever
Ignore wait-forked-but-failed-child

Test will be fixed in #19588
auto merge of #19590 : sfackler/rust/fix-android, r=sfackler

Seems to be blocking forever
Fix false positive alerts from a run-pass test on Command.

Reported as a part of rust-lang/rust#19120

The logic of rust-lang/rust@74fb798a200dc82cf5b4a18065e3ea565229adc3 was
flawed because when a CI tool run the test parallely with other tasks,
they all belong to a single session family and the test may pick up
irrelevant zombie processes before they are reaped by the CI tool
depending on timing.

Also, panic! inside a loop over all children makes the logic simpler.

By not destructing the return values of Command::spawn() until
find_zombies() finishes, I believe we can conduct a slightly stricter
test.

Signed-off-by: NODA, Kai <nodakai@gmail.com>