Revoke, and then delete a certificate

This functionality is manually tested. because of heavy reliance on
server configuration and bash commands.

Ruby OpenSSL library lacks a good way to manage revocation list
programatically, which would be the best option to work with. We might
still use command line tools in the end.

app/controllers/admin/certificates_controller.rb

@@ -28,7 +28,7 @@ module Admin
     end
 
     def destroy
-      if @certificate.destroy
+      if @certificate.revoke! && @certificate.destroy
         flash[:notice] = I18n.t('record_deleted')
         redirect_to admin_api_user_path(@api_user)
       else

app/models/certificate.rb

@@ -127,6 +127,7 @@ class Certificate < ActiveRecord::Base
 
     self.class.update_registry_crl
     self.class.reload_apache
+    self
   end
 
   class << self