Avoid dangling partial image on size/checksum mismatch

Fixes bug 1122299

Previously, when the supplied image size or checksum didn't match
the calculated values, partial image image data was left dangling
in the backend store.

Now, we clean up when the mismatch is detected.

Change-Id: I916d78ef3b2065e87df31ec4fb405915417d68aa
Swallow UserWarning from glance-cache-manage

Fixes bug 1129445

Previously, we exposed internal technical debt as an apparent
user-facing warning.

Now the warning is swallowed in the internal case, but continues
to be seen by external users of this library.

Note that this fix is not relevant on master, as that the warning
no longer occurs in that case.

Change-Id: I30a835e0024acac8841b4746968abe7cae9e14cb
Prints list-cached dates in isoformat

Converts dates printed by list-cached to a human readable format
(isoformat). It now checks whether the image last_access time is == 0.0
and prints "Not Accessed Yet" if so.

* Updates openstack.common.timeutils
* Fixes bug 1102334

Change-Id: I6f60525d8419d45e6962b936a2661825b606cba2
Merge "Swallow UserWarning from glance-cache-manage" into stable/folsom
Merge "Avoid dangling partial image on size/checksum mismatch" into stable/folsom