fix-finding-query-methods

[picandocodigo]

Transferred from elastic/elasticsearch-ruby#855:

Original Pull Request message:

Queirs.const_defined? 'Foo' find not only Queries::Foo but also ::Foo,
so if program has Foo class, this method_missing call Foo.new instead of call foo method.

class Foo
   include ActiveModel::Model
   include ActiveModel::Attributes

   attribute :name, :string
end

class SearchForm
  include ActiveModel::Model
  include ActiveModel::Attributes
  include Elasticsearch::DSL

  attribute :foo

  def condition
    search do
      query do
        bool { must { term name: foo.name } }
      end
    end
  end
end

p SearchForm.new(foo: Foo.new(name: 'hello')).condition.to_hash

• expect: {:query=>{:bool=>{:must=>[{:term=>{:name=>"name"}}]}}}
• actual: {:query=>{:bool=>{:must=>[{:term=>{:name=>nil}}]}}}

[picandocodigo]

@masarakki would it be possible for you to add a test for this? Thanks!