test/extended/cli/mustgather: Local-only getPluginOutputDir
test/extended/cli/mustgather: Local-only getPluginOutputDir

Removing the oc image calculations which we grew in 17b5a92349
(support old and new must-gather output, 2019-09-04, #23724).  This
pivot avoids failing on:

  imageId, ok := imageutil.ResolveLatestTaggedImage(stream, "latest")
  o.Expect(ok).To(o.BeTrue())

like [1] did.  Checking the contents of [1]'s must-gathers:

  $ curl -s https://gcsweb-ci.apps.ci.l2s4.p1.openshiftapps.com/gcs/origin-ci-test/pr-logs/pull/openshift_oc/833/pull-ci-openshift-oc-master-e2e-metal-ipi-ovn-ipv6/1396775908324413440/artifacts/e2e-metal-ipi-ovn-ipv6/gather-must-gather/artifacts/must-gather.tar | tar -tvz | head -n5
  drwx------ 1001210000/root   0 2021-05-24 05:38 .
  -rw------- 1001210000/root 3406540 2021-05-24 05:38 event-filter.html
  -rw------- 1001210000/root  758413 2021-05-24 05:38 must-gather.log
  drwxr-xr-x 1001210000/root       0 2021-05-24 05:38 registry-build02-ci-openshift-org-ci-op-s1s14k72-stable-sha256-f43d80e9d24970297d32fc572b7fdd8349e1700f64785c0ed3b7f75c15bc7750
  drwxr-xr-x 1001210000/root       0 2021-05-24 05:38 registry-build02-ci-openshift-org-ci-op-s1s14k72-stable-sha256-f43d80e9d24970297d32fc572b7fdd8349e1700f64785c0ed3b7f75c15bc7750/cluster-scoped-resources

and:

  $ curl -s https://gcsweb-ci.apps.ci.l2s4.p1.openshiftapps.com/gcs/origin-ci-test/pr-logs/pull/openshift_oc/833/pull-ci-openshift-oc-master-e2e-metal-ipi-ovn-ipv6/1396775908324413440/artifacts/e2e-metal-ipi-ovn-ipv6/gather-audit-logs/artifacts/audit-logs.tar | tar -tvz | head -n4
  drwx------ 1001210000/root   0 2021-05-24 05:41 .
  -rw------- 1001210000/root 3336 2021-05-24 05:41 event-filter.html
  drwxr-xr-x 1001210000/root    0 2021-05-24 05:41 registry-build02-ci-openshift-org-ci-op-s1s14k72-stable-sha256-f43d80e9d24970297d32fc572b7fdd8349e1700f64785c0ed3b7f75c15bc7750
  drwxr-xr-x 1001210000/root    0 2021-05-24 05:41 registry-build02-ci-openshift-org-ci-op-s1s14k72-stable-sha256-f43d80e9d24970297d32fc572b7fdd8349e1700f64785c0ed3b7f75c15bc7750/audit_logs

[1]: https://prow.ci.openshift.org/view/gs/origin-ci-test/pr-logs/pull/openshift_oc/833/pull-ci-openshift-oc-master-e2e-metal-ipi-ovn-ipv6/1396775908324413440

bparees/origin,gabemontero/origin,hroyrh/origin,mfojtik/origin,akram/origin,mahak/origin,hroyrh/origin,gabemontero/origin,soltysh/origin,xiuwang/origin,sallyom/origin,csrwng/origin,openshift/origin,JacobTanenbaum/origin,xiuwang/origin,JacobTanenbaum/origin,jsafrane/origin,jsafrane/origin,mahak/origin,mfojtik/origin,csrwng/origin,sallyom/origin,akram/origin,openshift/origin,xiuwang/origin,bparees/origin,coreydaley/origin,hroyrh/origin,JacobTanenbaum/origin,akram/origin,mfojtik/origin,coreydaley/origin,jsafrane/origin,gabemontero/origin,soltysh/origin,coreydaley/origin,openshift/origin,mahak/origin,bparees/origin,deads2k/origin,deads2k/origin,deads2k/origin,soltysh/origin,sallyom/origin,csrwng/origin