telemetry: Fix killing the perf profiler
Telemetry was failing to kill the perf profiler on Android because
pylib's KillAll command didn't account for multiple instances of the
same binary being running. The KillAll function would randomly kill one
of the running instances and then time out waiting for the instances to
go away.
This patch changes pylib's KillAll helper send the signal to all running
instances instead of just one. To do that we need to extend the GetPids
function to return all running instances of a binary instead of just one.
BUG=512564
Review URL: https://codereview.chromium.org/
1254843002
Cr-Commit-Position: refs/heads/master@{#340496}