(#11413) Update dpkg query used by apt::force

(#11413) Update dpkg query used by apt::force

This patch fixes the query used by apt::force to
determine rather or not the package is installed.

Previously, the expression was not specific enough and
could not lead to false positives in cases where a package
name is contained within another package name (puppet could be
incorrectly determined as being installed if puppet-common is
installed)

This commit resolves that by improving the query expression.