Always pass CVV on card update for Braintree Blue

Always passing the CVV allows for "updating a credit card and explicitly
verifying the card" at the same time:
https://www.braintreepayments.com/docs/ruby/general/card_verification#credit_card_api

lib/active_merchant/billing/gateways/braintree_blue.rb

@@ -105,6 +105,7 @@ def update(vault_id, creditcard, options = {})
           credit_card_params = merge_credit_card_options({
             :credit_card => {
               :number => creditcard.number,
+              :cvv => creditcard.verification_value,
               :expiration_month => creditcard.month.to_s.rjust(2, "0"),
               :expiration_year => creditcard.year.to_s
             }

test/unit/gateways/braintree_blue_test.rb

@@ -150,6 +150,36 @@ def test_store_with_billing_address_options
     @gateway.store(credit_card("41111111111111111111"), :billing_address => billing_address)
   end
 
+  def test_update_with_cvv
+    stored_credit_card = mock(:token => "token", :default? => true)
+    customer = mock(:credit_cards => [stored_credit_card], :id => '123')
+    Braintree::Customer.stubs(:find).with('vault_id').returns(customer)
+    BraintreeBlueGateway.any_instance.stubs(:customer_hash)
+
+    result = Braintree::SuccessfulResult.new(:customer => customer)
+    Braintree::Customer.expects(:update).with do |vault, params|
+      assert_equal "567", params[:credit_card][:cvv]
+      [vault, params]
+    end.returns(result)
+
+    @gateway.update('vault_id', credit_card("41111111111111111111", :verification_value => "567"))
+  end
+
+  def test_update_with_verify_card_true
+    stored_credit_card = mock(:token => "token", :default? => true)
+    customer = mock(:credit_cards => [stored_credit_card], :id => '123')
+    Braintree::Customer.stubs(:find).with('vault_id').returns(customer)
+    BraintreeBlueGateway.any_instance.stubs(:customer_hash)
+
+    result = Braintree::SuccessfulResult.new(:customer => customer)
+    Braintree::Customer.expects(:update).with do |vault, params|
+      assert_equal true, params[:credit_card][:options][:verify_card]
+      [vault, params]
+    end.returns(result)
+
+    @gateway.update('vault_id', credit_card("41111111111111111111"), :verify_card => true)
+  end
+
   def test_merge_credit_card_options_ignores_bad_option
     params = {:first_name => 'John', :credit_card => {:cvv => '123'}}
     options = {:verify_card => true, :bogus => 'ignore me'}