(maint) Fix acceptance tests for ssh_authorize_key

Currently the query acceptance test for ssh_authorize_key was blocked by
PUP-1605 because there was not a specified user for the resource to know
what authorize_keys file to use. The acceptance test was there for not
running at all.

This commit specifies root as the user to use for the test so that the
test can actually be run without failing out. It also uses puppet where
possible to verify instead of relying on system functions.