BZ 1114143 Added host provisioning cancel message when cancelled by the user

If a user canceled a host provision request the user was presented with "Add of new Host Request was cancelled by the user" created a new message for the host provision cancel action "Provision Host Request was cancelled by the user".

https://bugzilla.redhat.com/show_bug.cgi?id=1114143
Josh, you can refactor this to eliminate rubycop warnings as:
```ruby
  page.redirect_to(:action    => 'show_list',
                   :flash_msg => I18n.t("flash.host.provision_cancelled",
                                        :model => ui_lookup(:model => "Host")))

```