throw SecurityException in isProviderEnabled()

In MR0, we did not allow applications to query enabled status of
location providers they did not have permission to use. Some
applications counted on this behavior, using the thrown
SecurityException to determine whether or not they have permission
to use the specified provider.

Reverting to this behavior fixes the regressions seen in those
applications.

Bug: 7251459
Change-Id: I8b0cfd5862c80f0c831a4ab544c3fa7408bc84a0