fix dpkg shell_out error

removing the inheritance from apt package removed the include
of the shell_out command
Prevent indentation from being set to negative numbers

If we don't defensively program here, the result is terrible.  All that
gets raised is "negative argument" from deep within the formatter and
from then on the formatter is broken.  It will continue to raise errors
from events called from inside the Chef::Client exception handler and
you're gonna have a bad time.
add note on why commented line is commented
Merge pull request #1720 from opscode/lcg/fix-dpkg

Lcg/fix dpkg