Accurately check image names to ensure we pull a box if present
Accurately check image names to ensure we pull a box if present

This fixes the "Couldn't open file /tmp/omv/centos-7.1" errors that
would be seen if you didn't have a centos-7.1 box, but did have a
centos-7.1-docker box.

purpleidea/oh-my-vagrant,LalatenduMohanty/oh-my-vagrant,mairin/oh-my-vagrant,gpjonesii/oh-my-vagrant,purpleidea/oh-my-vagrant,goern/oh-my-vagrant,mairin/oh-my-vagrant,LalatenduMohanty/oh-my-vagrant,LalatenduMohanty/oh-my-vagrant,bhalothia/oh-my-vagrant,geekcheng/oh-my-vagrant,geekcheng/oh-my-vagrant,goern/oh-my-vagrant,gpjonesii/oh-my-vagrant,gpjonesii/oh-my-vagrant,mairin/oh-my-vagrant,geekcheng/oh-my-vagrant,bhalothia/oh-my-vagrant,goern/oh-my-vagrant,br0ziliy/oh-my-vagrant,bhalothia/oh-my-vagrant,br0ziliy/oh-my-vagrant,br0ziliy/oh-my-vagrant,purpleidea/oh-my-vagrant