Currently, divingbell-apt will only remove packages that aren't
on the current requested package list when they were previously
installed by divingbell-apt. This patchset adds a "strict" mode
which causes it to remove packages not on the requested package
list regardless of whether divingbell installed them (i.e., it
can remove unwanted packages that were part of the host's base
image).
Change-Id: Ie2ba5d47646bfaaf030cb54673e644ab0e917fd4
44525162a5