android: Stop child process in GetTerminationInfo

Android currently abuses TerminationStatus to pass whether process is
"oom protected" rather than whether it has died or not. This confuses
cross-platform code about the state process.

Only TERMINATION_STATUS_STILL_RUNNING is treated as still running, which
android never passes. Also it appears to be ok to kill the process in
getTerminationInfo as it's only called when the child process is dead or
dying. Also posix kills the process on some calls.

Bug: 940245
Change-Id: Id165711848c279bbe77ef8a784c8cf0b14051877
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1516284
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: ssid <ssid@chromium.org>
Commit-Queue: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639639}