ci: force a particular ceph version

Let's force v16.2.5 since the CI is broken with 16.2.6. This gives us
time to continue to merge work and work on fixing deployments with
16.2.6 in parallel.

Signed-off-by: Sébastien Han <seb@redhat.com>

cluster/examples/kubernetes/ceph/cluster-test.yaml

@@ -28,7 +28,7 @@ metadata:
 spec:
   dataDirHostPath: /var/lib/rook
   cephVersion:
-    image: quay.io/ceph/ceph:v16
+    image: quay.io/ceph/ceph:v16.2.5
     allowUnsupported: true
   mon:
     count: 1

tests/framework/installer/ceph_installer.go

@@ -50,7 +50,7 @@ const (
 	// test with the latest octopus build
 	octopusTestImage = "quay.io/ceph/ceph:v15"
 	// test with the latest pacific build
-	pacificTestImage = "quay.io/ceph/ceph:v16"
+	pacificTestImage = "quay.io/ceph/ceph:v16.2.5"
 	// test with the latest master image
 	masterTestImage    = "ceph/daemon-base:latest-master-devel"
 	cephOperatorLabel  = "app=rook-ceph-operator"