Propagate KUBECTL_PRUNE_WHITELIST_OVERRIDE to master kube-env

Author: tosi3k

cluster/gce/util.sh

@@ -1346,6 +1346,7 @@ ETCD_CA_CERT: $(yaml-quote ${ETCD_CA_CERT_BASE64:-})
 ETCD_PEER_KEY: $(yaml-quote ${ETCD_PEER_KEY_BASE64:-})
 ETCD_PEER_CERT: $(yaml-quote ${ETCD_PEER_CERT_BASE64:-})
 SERVICEACCOUNT_ISSUER: $(yaml-quote ${SERVICEACCOUNT_ISSUER:-})
+KUBECTL_PRUNE_WHITELIST_OVERRIDE: $(yaml-quote ${KUBECTL_PRUNE_WHITELIST_OVERRIDE:-})
 EOF
     # KUBE_APISERVER_REQUEST_TIMEOUT_SEC (if set) controls the --request-timeout
     # flag