Use a more suitable method of detecting if authentication is needed

The `db.serverCmdLineOpts()` method always requires authentication when
auth is enabled. It doesn't take the `enableLocalAuthBypass` parameter
into account, the subsequent authentication attempt always fails if a
user doesn't exists. This commit switches to the `rs.status()` method,
as that method does take the `enableLocalAuthBypass` parameter into
account and allows us to obtain a shell before with authentication
enabled, but before the user exists.

Author: stevenpost

templates/mongoshrc.js.erb

@@ -19,13 +19,15 @@ function rsReconfigSettings(settings){
 <% if @auth and @store_creds -%>
 function authRequired() {
   try {
-    return db.serverCmdLineOpts().ok != 1;
+    return rs.status().ok != 1;
   } catch (err) {
     if (err.message.match(/requires authentication/) || err.message.match(/not authorized on admin/)) {
       return true
-    } else {
-      throw("Unknown error :" + err)
+    if (err.message.match(/not running with --replSet/)) {
+      return false
     }
+    throw("Unknown error :" + err)
+  }
   }
 }