Do not throw on call to isTetheringSupported w/o permission

...just return false instead.

Test: Made an app to test this. Made sure it doesn't have
Test: the required permission. Checked it crashes with
Test: SecurityException without this change. Checked that it
Test: doesn't with it.

Merged-In: Ib5b17a7f68c1327f47fe1f54c0454c51f4226907
Change-Id: Id20d3c240ec5d70d085e0366b92ab3a514f3e7c8
(cherry picked from commit 8f76fc38)