Update rook/ceph Docker tag to v1.9.1

This MR contains the following updates:

Package	Type	Update	Change
rook/ceph	ironbank-docker	minor	v1.6.8 -> v1.9.1
rook/ceph		minor	v1.6.8 -> v1.9.1
rook/ceph	stage	minor	v1.6.8 -> v1.9.1

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