Lazily unmount persistent volumes in DockerContainerizer.
Lazily unmount persistent volumes in DockerContainerizer.

Use MNT_DETACH to unmount persistent volumes in DockerContainerizer to
workaround an issue of incorrect handling of container destroy
failures. Currently, if unmount fails there, the containerizer will
still treat the container as terminated, and the agent will schedule
the cleanup of the container's sandbox. Since the mount hasn't been
removed in the sandbox (e.g., due to EBUSY), that'll result in data in
the persistent volume being incorrectly deleted. Use MNT_DETACH so
that the mount point in the sandbox will be removed immediately. See
MESOS-7366 for more details.

Review: https://reviews.apache.org/r/58279

andschwa/mesos,abudnik/mesos,craimbert/mesos,kaysoky/mesos,abudnik/mesos,jpeach/mesos,asamerh4/mesos,dforsyth/mesos,andschwa/mesos,jpeach/mesos,Gilbert88/mesos,zmalik/mesos,chhsia0/mesos,kaysoky/mesos,chhsia0/mesos,gsantovena/mesos,asamerh4/mesos,gsantovena/mesos,neilconway/mesos,jpeach/mesos,abudnik/mesos,andschwa/mesos,verizonlabs/mesos,chhsia0/mesos,kaysoky/mesos,jpeach/mesos,reneploetz/mesos,craimbert/mesos,reneploetz/mesos,Gilbert88/mesos,neilconway/mesos,verizonlabs/mesos,verizonlabs/mesos,reneploetz/mesos,abudnik/mesos,Gilbert88/mesos,asamerh4/mesos,kaysoky/mesos,gsantovena/mesos,andschwa/mesos,zmalik/mesos,neilconway/mesos,gsantovena/mesos,reneploetz/mesos,andschwa/mesos,chhsia0/mesos,asamerh4/mesos,dforsyth/mesos,jpeach/mesos,dforsyth/mesos,chhsia0/mesos,craimbert/mesos,craimbert/mesos,zmalik/mesos,zmalik/mesos,zmalik/mesos,dforsyth/mesos,andschwa/mesos,Gilbert88/mesos,reneploetz/mesos,Gilbert88/mesos,Gilbert88/mesos,abudnik/mesos,verizonlabs/mesos,abudnik/mesos,verizonlabs/mesos,dforsyth/mesos,kaysoky/mesos,asamerh4/mesos,gsantovena/mesos,abudnik/mesos,dforsyth/mesos,craimbert/mesos,andschwa/mesos,neilconway/mesos,verizonlabs/mesos,craimbert/mesos,gsantovena/mesos,neilconway/mesos,jpeach/mesos,dforsyth/mesos,gsantovena/mesos,verizonlabs/mesos,asamerh4/mesos,reneploetz/mesos,craimbert/mesos,kaysoky/mesos,zmalik/mesos,jpeach/mesos,neilconway/mesos,chhsia0/mesos,kaysoky/mesos,reneploetz/mesos,Gilbert88/mesos,neilconway/mesos,chhsia0/mesos,asamerh4/mesos,zmalik/mesos