Revert "Remove deployment::target"

This reverts commit 7d05ab065cf9581a4399706ee99b0601067ef8ec.

The trebuchet provider sets the wrong deployment_target grain; until that's fixed, using this class is the workaround. Adding new hosts as targets of a repo for certain repos will trigger this bug.

Info on the bug:

Grains corresponding to repos are defined in role::deployment::config, see $repo_config.  Several repos under the same base might use the same grain or they might not; see integration and analytics as two examples.  The custom package provider always uses base (i.e. the parent dir) as the grain name, which matches some configs by luck but many it doesn't.

Those configs wind up in /etc/salt/deploy_runner.conf on the salt master, explicitly checked by the trebuchet runner. How the custom package provider is going to get at those, I really don't know.

Note that testing the custom provider on hosts already targets of a repo would have left the old correct grain in place, so the failure wouldn't have shown up.

Change-Id: I18b329fd2f35818167e3db6b3ab77f82d4cf4a94