qa/tasks/rook: add testing for host label add/rm

This commit adds simple tests that check if the orchestrator
can add and remove labels from nodes.

Signed-off-by: Joseph Sawaya <jsawaya@redhat.com>

qa/suites/orch/rook/smoke/2-workload/radosbench.yaml

@@ -3,3 +3,10 @@ tasks:
     host.a:
 - radosbench:
     clients: [client.a]
+- rook.shell:
+    commands:
+        - |
+          ceph orch host label add `hostname` foo
+          ceph orch host ls | grep foo
+          ceph orch host label rm `hostname` foo
+          ceph orch host ls | grep -v foo