Remove dangling example-tenants secret on undeploy.
Remove dangling example-tenants secret on undeploy.

The example tenants secret is used to initialize the device registry
volume with the DEFAULT_TENANT. Once the volume is created, the secret
is no longer necessary and should be deleted during undeploy in order to
allow for an updated version of the example tenants to be used in a
future initialization process.

Signed-off-by: Kai Hudalla <6c3288b94355003a6c5f12ba233f9fc06ef02a62@bosch-si.com>
dejanb/hono,dejanb/hono,dejanb/hono