Bug 1560402 - Pass the wanted account manager pane via openPreferencesTab() properly. r=jorgk

mailnews/base/content/msgAccountCentral.js

@@ -268,7 +268,7 @@ function ComposeAMessage(event) {
  *                    'am-addressing.xul', 'am-smtp.xul'
  */
 function ViewSettings(selectPage) {
-  window.parent.MsgAccountManager(selectPage);
+  window.parent.MsgAccountManager(selectPage, selectedServer);
 }
 
 // Open AccountWizard to create an account

mailnews/base/prefs/content/AccountManager.js

@@ -1513,6 +1513,7 @@ var gAccountTree = {
   },
 
   _build() {
+    currentAccount = currentPageId = null;
     var bundle = document.getElementById("bundle_prefs");
     function getString(aString) { return bundle.getString(aString); }
     var panels = [{string: getString("prefPanel-server"), src: "am-server.xul"},

mailnews/base/prefs/content/accountUtils.js

@@ -239,7 +239,7 @@ function MsgAccountManager(aSelectPage, aServer) {
 
   if (AppConstants.MOZ_APP_NAME == "thunderbird") {
     // Load the Account Manager in a tab.
-    openPreferencesTab("paneAccount", aServer ? aServer.key : null, aSelectPage);
+    openPreferencesTab("paneAccount", aServer ? aServer.key : null, { subdialog: aSelectPage });
   } else {
     // If the Account Manager is already running, just focus the right server.
     let existingAccountManager = Services.wm.getMostRecentWindow("mailnews:accountmanager");