Remove the Mock chroot in case "init" or "install" phase fails.
    
    So far we only removed the Mock chroot after the "run" phase, but in
    case there is some issue before we even get to that phase during the
    Mock "init" or "install" phases, the chroot data would remain on
    filesystem forever.
    
    In this commit, this is fixed by catching any issue in "init" and
    "install" phases and removing the Mock chroot before re-raising.