(PUP-3035) Add /var/run/puppet to debian packaging

Previously /var/run/puppet was created only during service start on
debian for both puppet and puppetmaster services. However, as it is used
in both of those services, it makes sense to have it owned and created
by one of the puppet packages. puppet-common is a dependency of both the
puppet and puppetmaster packages, so this commit adds /var/run/puppet to
the puppet-common.dirs file so it will be created in that package. This
also brings parity between redhat and debian packages in this respect,
as redhat puppet packages create the /var/run/puppet directory already.
This also adds a dpkg-statoverride call to manage permissions for the
/var/run/puppet directory.
(PUP-3035) Refactor dpkg-statoverride calls in puppet-common.postinst

This commit does some simple refactoring int he puppet-common.postinst
to avoid some unneeded repetition.
Merge pull request #3001 from haus/ticket/master/pup-3035-add-var-run-puppet-to-debian-packaging

(PUP-3035) Add /var/run/puppet to debian packaging