Improve e2e testcase for RHCOS

[vikin91]

This is a follow-up to #1004.
In the test case, we need a package that has high probability of being free from vulnerabilities because we assert on it to be recognized by scanner and have exactly 0 vulnerabilities.

In this PR, I replace the previously used grep by tzdata guesstimating that the chance of finding a vulnerability in the latter is lower than in the former.

Tested

On CI and locally with:

• make image deploy-local
• Opening a port-forward to scanner:8443
• Running go test -tags e2e -timeout=10s -count=1 -v -run ^TestGRPCGetRHCOSNodeVulnerabilities$ github.com/stackrox/scanner/e2etests

[ghost]

Images are ready for the commit at 9176389.

To use the images, use the tag 2.27.x-22-g9176389cd2.

[vikin91]

The modified test case passed in CI. All failures in the recent CI run are unrelated.

[msugakov]

/retest

[RTann]

I think another option is to add some flag to the test to indicate if you want to bother looking at the vuln data or not (or even just check for specific vulns). We have this precedent set in other parts of the e2e tests (see testcase_test.go)

[openshift-ci]

@vikin91: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/slim-e2e-tests	9176389	link	false	/test slim-e2e-tests
ci/prow/e2e-tests	9176389	link	false	/test e2e-tests

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[vikin91]

Thanks Ross! I see that I would need to introduce such flag like onlyCheckSpecifiedVulns bool on the vulnerability level - so each expected feature would need to have an indicator whether we assert on vulnerabilities using isSubset or equals.

I will give it a try a separate PR to keep this change small.