cluster: Allow kubevirtci tag overriding

It is helpful either manually or for example
when used from CNAO, to use same tag of the cluster that CNAO deployed.
Otherwise a kubevirtci tag mismatch can cause failures once running from CNAO.

Signed-off-by: Or Shoval <[email protected]>

Author: oshoval

cluster/cluster.sh

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 export KUBEVIRT_PROVIDER=${KUBEVIRT_PROVIDER:-'k8s-1.26-centos9'}
-export KUBEVIRTCI_TAG=2305081329-48e913c
+export KUBEVIRTCI_TAG=${KUBEVIRTCI_TAG:-2305081329-48e913c}
 
 KUBEVIRTCI_REPO='https://github.com/kubevirt/kubevirtci.git'
 # The CLUSTER_PATH var is used in cluster folder and points to the _kubevirtci where the cluster is deployed from.