Support running multiple wa workloads/processes simultaneously

[chrisswinchatt-arm]

I am using two wa processes to stress a device in different ways at the same time. One needs to be programmatically turned on and off in response to a condition. Currently how I'm doing that is to start one of the workloads in one wa process, and when the condition is true, start another wa process which runs the other workload until the condition becomes false and I kill the second wa process.

Having two processes seems cause issues where one of the processes tries to execute busybox and triggers an exception:

TargetStableCalledProcessError: Command '...' returned non-zero exit status 126.
STDOUT: 
STDERR: /system/bin/sh: /data/local/tmp/bin/busybox: can't execute: Permission denied

[marcbonnici]

Hi,

This is not an expected use case to use multiple instances of WA to manage the same device concurrently as WA expects to configure the device to a known state (deploying binaries etc.) upon initialization which I expect would conflict with other already running instances where such binaries may already be in use.

Would it be possible to merge these scenarios into a single workload that uses external input to control the flow rather than killing / starting a new instance?