[Java.Interop] Do not dispose the return value

Do not dispose the return valueat at all. Not even using
`DisposeUnlessReferenced`, becuse that would dispose the IJavaPeerable
object and not just the reference.

Author: radekdoulik

src/Java.Interop.Export/Tests/Java.Interop/MarshalMemberBuilderTest.cs

@@ -477,14 +477,6 @@ public void CreateMarshalFromJniMethodExpression_FuncIJavaObject ()
 	}
 	finally
 	{
-		if (null != __mret)
-		{
-			__mret.DisposeUnlessReferenced();
-		}
-		else
-		{
-			default(void);
-		}
 		__envp.Dispose();
 	}
 }");

src/Java.Interop/Java.Interop/JniRuntime.JniValueManager.cs

@@ -592,6 +592,7 @@ public override void DestroyGenericArgumentState (IJavaPeerable value, ref JniVa
 		public override Expression CreateParameterFromManagedExpression (JniValueMarshalerContext context, ParameterExpression sourceValue, ParameterAttributes synchronize)
 		{
 			var r = CreateIntermediaryExpressionFromManagedExpression (context, sourceValue);
+			context.CleanupStatements.Add (DisposeObjectReference (r));
 
 			var h = Expression.Variable (typeof (IntPtr), sourceValue.Name + "_handle");
 			context.LocalVariables.Add (h);
@@ -609,9 +610,6 @@ Expression CreateIntermediaryExpressionFromManagedExpression (JniValueMarshalerC
 						test:       Expression.Equal (Expression.Constant (null), sourceValue),
 						ifTrue:     Expression.Assign (r, Expression.New (typeof (JniObjectReference))),
 						ifFalse:    Expression.Assign (r, Expression.Property (sourceValue, "PeerReference"))));
-			context.CleanupStatements.Add (Expression.IfThen (
-						test:       Expression.NotEqual (Expression.Constant (null), sourceValue),
-						ifTrue:     Expression.Call (sourceValue, typeof (IJavaPeerable).GetTypeInfo ().GetDeclaredMethod ("DisposeUnlessReferenced"))));
 
 			return r;
 		}

src/Java.Interop/Tests/Java.Interop/JniValueMarshalerContractTests.cs

@@ -608,14 +608,7 @@ protected override string GetExpectedReturnValueFromManagedExpression (string jv
 	}}
 	finally
 	{{
-		if (null != __value)
-		{{
-			__value.DisposeUnlessReferenced();
-		}}
-		else
-		{{
-			default(void);
-		}}
+		default(void);
 	}}
 }}";
 		}