agent: display messages from serf in cli (#5236)

* display messages from serf in cli

api/operator_keyring.go

@@ -16,6 +16,9 @@ type KeyringResponse struct {
 	// Segment has the network segment this request corresponds to.
 	Segment string
 
+	// Messages has information or errors from serf
+	Messages map[string]string `json:",omitempty"`
+
 	// A map of the encryption keys to the number of nodes they're installed on
 	Keys map[string]int
 

command/keyring/keyring.go

@@ -154,6 +154,11 @@ func (c *cmd) handleList(responses []*consulapi.KeyringResponse) {
 
 		c.UI.Output("")
 		c.UI.Output(pool + ":")
+
+		for from, msg := range response.Messages {
+			c.UI.Output(fmt.Sprintf("  ===> %s: %s", from, msg))
+		}
+
 		for key, num := range response.Keys {
 			c.UI.Output(fmt.Sprintf("  %s [%d/%d]", key, num, response.NumNodes))
 		}