Review and ensure that we always correctly detect Debian package file

[pombredanne]

I observed as an anecdote that we may some issues to properly assign some files to Debian system packages in some Docker images.
I will come with a test case.

[pombredanne]

docker://r-base:latest is a good test case

[Monal-Reddy]

I would like to investigate this issue. I will attempt to reproduce it using docker://r-base:latest and report findings.