apt: allow specifying dpkg options

This will allow specifying dpkg options as a string passed over to apt
command. dpkg_options expects a comma-separated string of options to be
passed as dpkg options which will be further expanded. For example
dpkg_options='force-confdef,force-confold' will end up as
-o \"Dpkg::Options::=--force-confold\" when passed to apt
Example usage would be:
-m apt -u ubuntu -s \
 -a "upgrade=dist update_cache=yes dpkg_options='force-confold'"
or
apt: upgrade=dist update_cache=yes dpkg_options='force-confold'
Merge pull request #4358 from eslng/apt_add_dpkg_options

apt: allow specifying dpkg options