[authentication] fix authentication function

Author: Johan De Wit

templates/mongoshrc.js.erb

@@ -19,7 +19,7 @@ function rsReconfigSettings(settings){
 <% if @auth and @store_creds -%>
 function authRequired() {
   try {
-    return db.serverCmdLineOpts().code == 13;
+    return db.serverCmdLineOpts().ok != 1;
   } catch (err) {
     if (err.message.match(/requires authentication/) || err.message.match(/not authorized on admin/)) {
       return true
@@ -35,7 +35,7 @@ if (authRequired()) {
   db.getMongo().setReadPref('primaryPreferred')
   <%- end -%>
   try {
-    var prev_db = db
+    var prev_db = db.getName()
     db = db.getSiblingDB('admin')
     db.auth('<%= @admin_username %>', '<%= @admin_password_unsensitive %>')
     db = db.getSiblingDB(prev_db)