Handle httpChecksum.requestChecksumRequired trait (#4037)

Author: trivikr

lib/model/operation.js

@@ -23,7 +23,12 @@ function Operation(name, operation, options) {
       (operation.endpointdiscovery.required ? 'REQUIRED' : 'OPTIONAL') :
     'NULL'
   );
-  property(this, 'httpChecksumRequired', operation.httpChecksumRequired, false);
+
+  // httpChecksum replaces usage of httpChecksumRequired, but some APIs
+  // (s3control) still uses old trait.
+  var httpChecksumRequired = operation.httpChecksumRequired
+    || (operation.httpChecksum && operation.httpChecksum.requestChecksumRequired);
+  property(this, 'httpChecksumRequired', httpChecksumRequired, false);
 
   memoizedProperty(this, 'input', function() {
     if (!operation.input) {