init container blocks due to operator exec request got 137 error

[Yang Kelvin Liu]

application-mariadb-k8s: 23:25:18 ERROR juju.worker.uniter resolver loop error: executing operation "remote init": command terminated with exit code 137

Re-produces steps:

1. bootstrap and deploy some workload to 2.8;
2. upgrade charm;
3. the workload pod now always waits to init;
4. the above error message occurs in model log;
5. run juju scale, new pods are all waiting to be initialised;

# kill the operator, new operator recovers everything.

[Yang Kelvin Liu (kelvin.liu)]

https://github.com/juju/juju/pull/11566 will be landed to 2.8-rc2 to fix it.