Back out "[TM] Check TurboModules first in TurboModuleRegistry"

Summary:
`hg backout  D15703655`

possible cause of S180976

Reviewed By: shergin

Differential Revision: D15831550

fbshipit-source-id: 9080222c51e39f4432f4c081a8863dea2dcadec3

Author: logandaniels

Libraries/TurboModule/TurboModuleRegistry.js

@@ -17,19 +17,17 @@ import invariant from 'invariant';
 const turboModuleProxy = global.__turboModuleProxy;
 
 export function get<T: TurboModule>(name: string): ?T {
-  if (turboModuleProxy != null) {
-    const module: ?T = turboModuleProxy(name);
-    if (module != null) {
-      return module;
-    }
-  }
-
   // Backward compatibility layer during migration.
   const legacyModule = NativeModules[name];
   if (legacyModule != null) {
     return ((legacyModule: any): T);
   }
 
+  if (turboModuleProxy != null) {
+    const module: ?T = turboModuleProxy(name);
+    return module;
+  }
+
   return null;
 }