[Bug 1037634] The devicemapper volumes are not removed after container is removed

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1037634

Alexander Larsson  changed:

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--- Comment #2 from Alexander Larsson  ---
There are two issues here. 
First, there is a bug where we never remove the -init layers. 
And secondly, there are mounts for the images, which will go away if you remove
them (rmi), but these mounts are kinda unnecessary as they are not currenly in
use, and we should probably unmount them to keep the system "cleaner".