Don't try to template the packaging dir in the template task

The template task currently tries to template everything in the packaging repo
as well as in the project's ext dir, which means we're evaluating things we
don't necessarily want to. This commit explicitly excludes the packaging repo
from the list of dirs to search for erb templates to evaluate.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Merge pull request #168 from MosesMendoza/maint/master/dont_erb_packaging

Don't try to template the packaging dir in the template task