Suppress MSI/MSM validation when building remoting MSI.

I believe this will unblock a required migration in our signing
infrastructure.

BUG=none
R=garykac@chromium.org

Review URL: https://codereview.chromium.org/1020823003

Cr-Commit-Position: refs/heads/master@{#321438}

remoting/host/installer/win/parameters.json

@@ -23,6 +23,7 @@
   "light": {
     "switches": [
       "-cultures:en-us",
+      "-sval",
       "-sw1076"
     ]
   }