Update quay.io/coreos/clair Docker tag to v4

This MR contains the following updates:

Package	Type	Update	Change
quay.io/coreos/clair	ironbank-docker	major	v2.1.7 -> v4.1.0
quay.io/coreos/clair		major	v2.1.7 -> v4.1.0
quay.io/coreos/clair	stage	major	v2.1.7 -> v4.1.0

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