ceph-dev-*build: remove ceph-container after done with it

ceph-dev-*build: remove ceph-container after done with it

because `ceph-container` contains the artifacts created using `root`
user after 6090e4d00c82b8aba1d56ed249f29352e7c308d6, for instance, the
`staging` directory is created by
https://github.com/ceph/ceph-container/blob/2f61465f6a91f15470ff4f87844c5fe9c64b9664/maint-lib/stage.py#L102

so we need to remove `ceph-container` after pushing the created image
using `sudo` as well. otherwise, jenkins is not able to cleanup the
workspace using the "jenkins-build" user.

Signed-off-by: Kefu Chai <kchai@redhat.com>