Fix ports.installed state for pkg names that don't match origin

This fixes a bug where ``ports.installed`` states report failure to install,
due to the package name not matching the name of the port. For example,
if installing ``www/mod_perl2`` for use with ``www/apache22``, this results in a
package name of ``ap22-mod_perl2``. The ``ports.installed`` state thinks the
install failed because of this package name mismatch.

This fix checks the origin names of installed packages, instead of the
name of the package itself.