Add hostingsvcs.change_hostingserviceaccount perm to local-site admins.

On master, the unit tests for the remote repository resource are broken because
permission tests for the hostingsvcs.change_hostingserviceaccount permission
for local-site admins don't work. I'm not sure why this doesn't also break on
2.0.x, but either way this permission should be listed.

Testing done:
Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/6281/