Restore original 4.x behavior for initialization of function return name

Closes gh-25707

(cherry picked from commit 40bf83c9e5)

spring-jdbc/src/main/java/org/springframework/jdbc/core/metadata/CallMetaDataContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -355,7 +355,7 @@ public class CallMetaDataContext {
 							logger.debug("Using declared out parameter '" + paramName +
 									"' for function return value");
 						}
-						setFunctionReturnName(paramName);
+						this.actualFunctionReturnName = paramName;
 						returnDeclared = true;
 					}
 				}
@@ -393,8 +393,8 @@ public class CallMetaDataContext {
 								"Unable to locate declared parameter for function return value - " +
 								" add a SqlOutParameter with name '" + getFunctionReturnName() + "'");
 					}
-					else if (paramName != null) {
-						setFunctionReturnName(paramName);
+					else {
+						this.actualFunctionReturnName = param.getName();
 					}
 				}
 				else {
@@ -422,7 +422,7 @@ public class CallMetaDataContext {
 								(StringUtils.hasLength(paramNameToUse) ? paramNameToUse : getFunctionReturnName());
 						workParams.add(provider.createDefaultOutParameter(returnNameToUse, meta));
 						if (isFunction()) {
-							setFunctionReturnName(returnNameToUse);
+							this.actualFunctionReturnName = returnNameToUse;
 							outParamNames.add(returnNameToUse);
 						}
 						if (logger.isDebugEnabled()) {