plugin: fix process leak when Setup() fails

[sorindumitru]

We've noticed some leftover processes from vault plugins on our boxes. Some
of them were even left over from previous instances of the service and reparented
to init. This could cause issues if too many of them accumulate.

When running with TRACE logging the logs showed that there was an error return by
the call to Setup() the plugin. Looking through the code it looks like we do not
call Cleanup() in that case.

Before the patch our logs used to show this:

{"@level":"trace","@message":"setup","@module":"aplugin","@timestamp":"2020-06-30T11:42:42.110935-04:00","status":"started","transport":"gRPC"}
{"@level":"trace","@message":"setup","@module":"aplugin,"@timestamp":"2020-06-30T11:42:42.110986-04:00","err":"rpc error: code = Canceled desc = context canceled","status":"finished","took":50151,"transport":"gRPC"}

and after the patch we get the trace that the plugin has existed:

{"@level":"trace","@message":"setup","@module":"aplugin","@timestamp":"2020-07-02T05:27:02.065347-04:00","status":"started","transport":"gRPC"}
{"@level":"trace","@message":"setup","@module":"aplugin,"@timestamp":"2020-07-02T05:27:02.065386-04:00","err":"rpc error: code = Canceled desc = context canceled","status":"finished","took":39222,"transport":"gRPC"}
{"@level":"trace","@message":"cleanup","@module":"aplugin","@timestamp":"2020-07-02T05:27:02.065410-04:00","status":"started","transport":"gRPC"}
{"@level":"trace","@message":"cleanup","@module":"aplugin","@timestamp":"2020-07-02T05:27:02.065883-04:00","status":"finished","took":471538,"transport":"gRPC"}
{"@level":"warn","@message":"error closing client during Kill","@module":"aplugin","@timestamp":"2020-07-02T05:27:02.065929-04:00","err":"rpc error: code = Canceled desc = grpc: the client connection is closing"}
{"@level":"debug","@message":"plugin process exited","@module":"aaplugin","@timestamp":"2020-07-02T05:27:02.118913-04:00","error":"signal: killed","path":"...","pid":92276}

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[sorindumitru]

for the CLA, from what am I aware of this was already signed at the org level for the bloomberg org. Could the cla bot be checked to see if that org is in the allowed list?

[ncabatoff]

for the CLA, from what am I aware of this was already signed at the org level for the bloomberg org. Could the cla bot be checked to see if that org is in the allowed list?

I've opened a ticket with our helpdesk to sort that out.

[kalafut]

@sorindumitru Is the email address you used in your commits listed in your GitHub profile? I believe that's what the CLA bot checks.

[sorindumitru]

@kalafut Yes, it is. There was an additional check for that that failed initially, but was ok after I added it.

[ncabatoff]

Hi @sorindumitru,

Sorry for the continued hassle, but would you mind closing and re-submitting this PR? It sounds like that's the easiest way to move this forward.