Merge pull request #146 from pulp/rbarlow_remove_bw_test

Remove a unit test that didn't make good assertions, and that was non-de...
Merge pull request #148 from pulp/rbarlow-919519

Rbarlow 919519
920322 - Use import_units() inside of _import_pkg_category_unit() to ensure that we handle package groups correctly.
Fix 920322 a different way, without recursion.
Add a unit test to assert that we copy and correctly alter
package_groups during import.
Update the docblock for _import_pkg_group_unit().
Merge branch 'rbarlow-920322'