Mark Restricted APN connections as restricted.

If anything unrestricted is bundled in the whole thing has to be
unrestricted (we can't restrict based on destination or intent)
but the NOT_METERED flag wasn't taken into account.

This wasn't a problem before because telephony set that statically
and late, but a change caused it to be marked NOT_METERED earlier
which exposed this bug.

bug: 37208956
Test: new NetworkCapabilitiesTest.  Fails without fix, works with.
Change-Id: I7b7a1c38621ce0ecde8cf041e82b1ebb7a9c6f15