os/signal: TestStop/user_defined_signal_1 failing on android-arm{,64}-corellium builders

[bcmills]

I appear to have broken TestStop for SIGUSR1 in CL 226138.

I'm not sure why it's broken. I'll add a Skip for now.

2020-03-30T17:35:19-3ee782b/android-arm-corellium
2020-03-30T17:35:19-3ee782b/android-arm64-corellium

CC @ianlancetaylor

[gopherbot]

Change https://golang.org/cl/226458 mentions this issue: os/signal: in TestStop, skip the final "unexpected signal" check for SIGUSR1 on Android

[bcmills]

CL 203957 seems closely related (CC @aclements, @cherrymui, @mknyszek)

[gopherbot]

Change https://golang.org/cl/226461 mentions this issue: os/signal: make TestStop resilient to initially-blocked signals