Hotword: Decouple sometimes and always on prefs when disabling. They can both exist independently.

BUG=

Review URL: https://codereview.chromium.org/1011963002

Cr-Commit-Position: refs/heads/master@{#320896}

chrome/browser/search/hotword_service.cc

@@ -786,15 +786,12 @@ void HotwordService::SetAudioHistoryHandler(
 
 void HotwordService::DisableHotwordPreferences() {
   if (IsSometimesOnEnabled()) {
-    if (profile_->GetPrefs()->HasPrefPath(prefs::kHotwordSearchEnabled))
     profile_->GetPrefs()->SetBoolean(prefs::kHotwordSearchEnabled, false);
-  } else if (IsAlwaysOnEnabled()) {
-    if (profile_->GetPrefs()->HasPrefPath(
-            prefs::kHotwordAlwaysOnSearchEnabled)) {
+  }
+  if (IsAlwaysOnEnabled()) {
     profile_->GetPrefs()->SetBoolean(prefs::kHotwordAlwaysOnSearchEnabled,
                                      false);
   }
-  }
 }
 
 void HotwordService::OnHotwordSearchEnabledChanged(