Shutdown correctly if the extension is short lived

[a-cognet]

This is a follow up from #117

If the extension stops immediately after it starts, there could be a problem where shutdown happened before start. It's something we've seen in integration tests, but may happen or worsen the case where the extension is stuck in a restart loop with osqueryd.

I changed the Run function because it buried the original error and made the investigation harder.

Here is a stacktrace

Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: {"level":"warn","time":"2023-11-16T18:56:40.378Z","msg":"Shutting down client","extensionServer":"client","version":"1.29.1","pid":"2003","component":"osquery-plugin-server"}
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: panic: runtime error: invalid memory address or nil pointer dereference
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: [signal SIGSEGV: segmentation violation code=0x1 addr=0x58 pc=0x143f35b]
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: goroutine 43 [running]:
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: github.com/osquery/osquery-go.(*ExtensionManagerServer).Start.func1(0xc0001a2960, 0xc0002d7f88)
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: /go/src/XXXX/vendor/github.com/osquery/osquery-go/server.go:201 +0x13b
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: github.com/osquery/osquery-go.(*ExtensionManagerServer).Start(0x0?)
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: /go/src/XXXX/vendor/github.com/osquery/osquery-go/server.go:237 +0x25
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: github.com/osquery/osquery-go.(*ExtensionManagerServer).Run.func1()
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: /go/src/XXXX/vendor/github.com/osquery/osquery-go/server.go:251 +0x26
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: created by github.com/osquery/osquery-go.(*ExtensionManagerServer).Run
Nov 16 18:56:40 ip-.compute.internal osqueryd[1992]: /go/src/XXXX/vendor/github.com/osquery/osquery-
go/server.go:250 +0x85
Nov 16 18:56:40 ip-1.compute.internal systemd[1]: Stopped The osquery Daemon.

[a-cognet]

@directionless would you have any guidance on how I can get this PR reviewed? I could not find a procedure to follow. Thanks.

[directionless]

This seems reasonable. Though the subject here says "Panic" which I think is less desirable than the error return in the code. Is the PR subject out of date?

[a-cognet]

I updated the PR title with the intent, instead of stating the issue.