Remove checkPermission() call in getAllProviders().

getAllProviders() should return all locators, including those not
allowed or not enabled (according to the existing javadoc, at least).
The checkPermission() call prevented this behavior by throwing a
security exception. We restore the previous behavior by removing the
call.

Bug: 6950369

Change-Id: I0c6bc676d4c4db482bb68f1ab7fa5c93675118b4