Merge pull request #1971 from microsoft/rollforward-net-master

global.json: enable roll forward in .NET SDK (port to master)

Author: mjcheetham

global.json

@@ -1,7 +1,7 @@
 {
   "sdk": {
     "version": "10.0.203",
-    "rollForward": "disable"
+    "rollForward": "latestFeature"
   },
   "msbuild-sdks": {
     "Microsoft.Build.Traversal": "4.1.0",