Update quay.io/coreos/clair Docker tag to v2.1.7

This MR contains the following updates:

Package	Type	Update	Change
quay.io/coreos/clair	ironbank-docker	patch	v2.1.6 -> v2.1.7
quay.io/coreos/clair		patch	v2.1.6 -> v2.1.7
quay.io/coreos/clair	stage	patch	v2.1.6 -> v2.1.7

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