Fix zero-ordering SORT when called against lists

People mostly use SORT against lists, but our prior
behavior was pretending lists were an unordered bag
requiring a forced-sort when no sort was requested.

We can just use the native list ordering to ensure
consistency across replicaion and scripting calls.

Closes #2079
Closes #545 (again)

tests/unit/sort.tcl

@@ -246,6 +246,24 @@ start_server {
         r sort mylist by num get x:*->
     } {100}
 
+    test "SORT by nosort retains native order for lists" {
+        r del testa
+        r lpush testa 2 1 4 3 5
+        r sort testa by nosort
+    } {5 3 4 1 2}
+
+    test "SORT by nosort plus store retains native order for lists" {
+        r del testa
+        r lpush testa 2 1 4 3 5
+        r sort testa by nosort store testb
+        r lrange testb 0 -1
+    } {5 3 4 1 2}
+
+    test "SORT by nosort with limit returns based on original list order" {
+        r sort testa by nosort limit 0 3 store testb
+        r lrange testb 0 -1
+    } {5 3 4}
+
     tags {"slow"} {
         set num 100
         set res [create_random_dataset $num lpush]