oci-image-tool: Cleanup partially-unpacked directories on failures

[philips]

From @wking on September 1, 2016 18:16

We might want a switch to turn this off, but I think the default should be to remove the unpack directory if we fail partway through the unpack.

Spun off from here.

Copied from original issue: opencontainers/image-spec#242

[wking]

On Tue, Sep 20, 2016 at 07:48:16PM -0700, Brandon Philips wrote:

We might want a switch to turn this off, but I think the default
should be to remove the unpack directory if we fail partway through
the unpack.

PR is #7; we can close this issue.

[wking]

PR is #7; we can close this issue.

And #7 was merged back in October, so we can definitely close this issue ;).

Also related is the larger bundle cleanup (vs. just the unpacked rootfs cleanup) floated in #172. But that's distinct from this issue, so I see no reason to leave this issue open.

[zhouhao3]

As @wking said, closing this issus.