title: Mongoid Query Embedded Document Return Wrong Record
body: <p>I have two models <code>Core::User</code> and <code>Core::UserMeta</code> :</p>
  
  <pre><code>class Core::User
     include Mongoid::Document
  
     embeds_many :core_user_meta, class_name: 'Core::UserMeta'
  end
  </code></pre>
  
  <pre><code>class Core::UserMeta
     include Mongoid::Document
  
     field :meta_key, type: String
     field :meta_value
  
     embedded_in :core_user, class_name: 'Core::User'
  end
  </code></pre>
  
  <p>I'm using 2 criterias for the query <code>Core::UserMeta</code> on <code>Core::User</code> looks like :</p>
  
  <pre><code>Core::User.where('core_user_meta.meta_key': 'roles', 'core_user_meta.meta_value': 'member').first
  </code></pre>
  
  <p>I want to get a record has criterias <code>"roles"</code> in <code>meta_key</code> <strong>and</strong> <code>["member"]</code> in <code>meta_value</code> but the result always, looks like I'm using <code>or</code> clause instead of <code>and</code> clause</p>
  
  <pre><code>#&lt;Core::User _id: BSON::ObjectId('5b961b07eea19009d397cfaf'), core_user_meta: [{"_id"=&gt;BSON::ObjectId('5b961b07eea19009d397cfb0'), "meta_key"=&gt;"nickname", "meta_value"=&gt;"member"}, {"_id"=&gt;BSON::ObjectId('5b961b07eea19009d397cfbb'), "meta_key"=&gt;"roles", "meta_value"=&gt;["subscriber"]}]&gt; 
  </code></pre>