Fix interface conversion panic during database creds revoke (#4850)

builtin/logical/database/backend_test.go

@@ -603,7 +603,7 @@ func TestBackend_basic(t *testing.T) {
 					"username":              credsResp.Data["username"],
 					"role":                  "plugin-role-test",
 					"db_name":               "plugin-test",
-					"revocation_statements": []string(nil),
+					"revocation_statements": []interface{}(nil),
 				},
 			},
 		})

builtin/logical/database/secret_creds.go

@@ -111,7 +111,9 @@ func (b *databaseBackend) secretCredsRevoke() framework.OperationFunc {
 			if statementsRaw, ok := req.Secret.InternalData["revocation_statements"]; !ok {
 				return nil, fmt.Errorf("error during revoke: could not find role with name %q or embedded revocation statement data", req.Secret.InternalData["role"])
 			} else {
-				statements.Revocation = statementsRaw.([]string)
+				for _, v := range statementsRaw.([]interface{}) {
+					statements.Revocation = append(statements.Revocation, v.(string))
+				}
 			}
 		}