Fix flaky e2e test

[MrSerth]

• Failed: https://github.com/openHPI/poseidon/actions/runs/9698681202/attempts/1
• Successful: https://github.com/openHPI/poseidon/actions/runs/9698681202/attempts/2

websocket_test.go:363: 
    	Error Trace:	/home/runner/work/poseidon/poseidon/tests/e2e/websocket_test.go:363
    	            				/home/runner/work/poseidon/poseidon/tests/e2e/websocket_test.go:170
    	            				/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.9.0/suite/suite.go:115
    	Error:      	Not equal: 
    	            	expected: 1
    	            	actual  : 0
    	Test:       	TestE2ETestSuite/TestCommandMakeEnvironmentVariables/0

• Failed: https://github.com/openHPI/poseidon/actions/runs/10672601360/job/29580481134
• Successful: https://github.com/openHPI/poseidon/actions/runs/10672601360/job/29580604118

=== RUN   TestE2ETestSuite/TestGetFileContent_Nomad/Permission_Denied
{"environment_id":"0","error":"unexpected EOF","level":"warning","msg":"Unexpected EOF for Execute","package":"nomad","runner_id":"0-8a48a4a7-6969-11ef-a609-000d3a600657","sentry-fingerprint":["nomad-unexpected-eof"],"time":"2024-09-02T20:25:50.041434Z"}
    runners_test.go:473: 
        	Error Trace:	/home/runner/work/poseidon/poseidon/tests/e2e/runners_test.go:473
        	            				/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.9.0/suite/suite.go:115
        	Error:      	Not equal: 
        	            	expected: 424
        	            	actual  : 200
        	Test:       	TestE2ETestSuite/TestGetFileContent_Nomad/Permission_Denied
    runners_test.go:476: 
        	Error Trace:	/home/runner/work/poseidon/poseidon/tests/e2e/runners_test.go:476
        	            				/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.9.0/suite/suite.go:115
        	Error:      	"" does not contain "file not found or insufficient permissions"
        	Test:       	TestE2ETestSuite/TestGetFileContent_Nomad/Permission_Denied

[mpass99]

The second flaky test event can be reduced to the known upstream bug discussed in #589.
This occurs not only in production, but also in our e2e tests. Until the upstream issue is fixed, we can identify this cause by the line {"environment_id":"0","error":"unexpected EOF","level":"warning","msg":"Unexpected EOF for Execute","package":"nomad","runner_id":"0-8a48a4a7-6969-11ef-a609-000d3a600657","sentry-fingerprint":["nomad-unexpected-eof"],"time":"2024-09-02T20:25:50.041434Z"}.

We might even consider bumping nomad#12198, as the non-official Docker SDK produces this bug and has not fixed it since its disclosure two months ago.

[MrSerth]

Thanks for looking into the e2e test suite and pointing out the unexpected EOF bug we saw. Bumping nomad#12198 is a good idea and I've just added an upvote to the issue myself. Still, this probably only a long-term solution, since swapping the entire library is likely pretty complex for Nomad.

In the meantime, we could also try bumping go-dockerclient#1076, which would help for the e2e tests and the production use. Until then, I assume we need to live with these sporadic occurrences...