pkg/cli/admin/upgrade/: Mention Upgradeable=False

When 'Upgradeable=False', the cluster-version operator will block
(usually) minor version bumps.  Sometimes it will block all version
bumps [1].  Users running 'oc adm upgrade' should be notified about
these conditions, so they are not surprised if they choose a target
and the CVO subsequently blocks the chosen update [2].

[1]: https://bugzilla.redhat.com/show_bug.cgi?id=1822844
[2]: https://bugzilla.redhat.com/show_bug.cgi?id=1874293

pkg/cli/admin/upgrade/upgrade.go

@@ -317,6 +317,10 @@ func (o *Options) Run() error {
 		}
 		fmt.Fprintln(o.Out)
 
+		if c := findCondition(cv.Status.Conditions, configv1.OperatorUpgradeable); c != nil && c.Status == configv1.ConditionFalse {
+			fmt.Printf(o.Out, "Upgradeable=False\n\n  Reason: %s\n  Message: %s\n\n", c.Reason, c.Message)
+		}
+
 		if len(cv.Status.AvailableUpdates) > 0 {
 			fmt.Fprintf(o.Out, "Updates:\n\n")
 			w := tabwriter.NewWriter(o.Out, 0, 2, 1, ' ', 0)