Fix flake where cross ns finalizer can't be removed

[akalenyu]

Signed-off-by: Alex Kalenyuk [email protected]

What this PR does / why we need it: We fail to remove the finalizer because the mutating webhook validates source ns exists, but source ns might not be around anymore, and that is absolutely fine if DV is marked for deletion. The "offending" test case is [test_id:4960].

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #

Special notes for your reviewer: https://prow.ci.kubevirt.io/view/gs/kubevirt-prow/pr-logs/pull/kubevirt_containerized-data-importer/2363/pull-containerized-data-importer-e2e-ceph-gc/1552213098473984000 https://prow.ci.kubevirt.io/view/gs/kubevirt-prow/pr-logs/pull/kubevirt_containerized-data-importer/2381/pull-containerized-data-importer-e2e-ceph-gc/1555211218673733632 https://prow.ci.kubevirt.io/view/gs/kubevirt-prow/pr-logs/pull/kubevirt_containerized-data-importer/2371/pull-containerized-data-importer-e2e-ceph-gc/1553016969739898880

Release note:

NONE

[akalenyu]

/test all

[awels]

How about a unit test making sure this is working as expected, like Should always accept mutate when dv is marked for deletion?

[akalenyu]

How about a unit test making sure this is working as expected, like Should always accept mutate when dv is marked for deletion?

good idea, done

[awels]

/lgtm @mhenriks any other thoughts?

[mhenriks]

/approve

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