Merge pull request #12442 from danieleva/12422-keyring

Allows keyring operations on client agents

.changelog/12442.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+agent: Allow client agents to perform keyring operations
+```

agent/keyring.go

@@ -233,9 +233,6 @@ func decodeStringKey(key string) ([]byte, error) {
 func (a *Agent) keyringProcess(args *structs.KeyringRequest) (*structs.KeyringResponses, error) {
 	var reply structs.KeyringResponses
 
-	if _, ok := a.delegate.(*consul.Server); !ok {
-		return nil, fmt.Errorf("keyring operations must run against a server node")
-	}
 	if err := a.RPC("Internal.KeyringOperation", args, &reply); err != nil {
 		return &reply, err
 	}