Bug 1573932 - Disable extended triplets for certain policies. r=Mardak

Differential Revision: https://phabricator.services.mozilla.com/D43095

--HG--
extra : moz-landing-system : lando

browser/components/enterprisepolicies/Policies.jsm

@@ -387,6 +387,7 @@ var Policies = {
     onBeforeAddons(manager, param) {
       if (param) {
         setAndLockPref("identity.fxaccounts.enabled", false);
+        setAndLockPref("trailhead.firstrun.branches", "nofirstrun");
       }
     },
   },
@@ -967,6 +968,7 @@ var Policies = {
     onProfileAfterChange(manager, param) {
       let url = param ? param.href : "";
       setAndLockPref("startup.homepage_welcome_url", url);
+      setAndLockPref("trailhead.firstrun.branches", "nofirstrun");
     },
   },