Update the way we change meteredness of cellular networks in tests.

SubscriptionManager.setSubscriptionOverrideUnmetered() has been updated
to add NET_CAPABILITY_TEMPORARILY_NOT_METERED instead of
NET_CAPABILITY_NOT_METERED. So, we can't rely on that for changing the
meteredness.

Bug: 179664982
Test: atest tests/cts/hostside/src/com/android/cts/net/HostsideRestrictBackgroundNetworkTests.java
Test: atest tests/cts/hostside/src/com/android/cts/net/HostsideNetworkCallbackTests.java
Change-Id: I4163b2f9c6f80b4e639d9977ef7e2b444ab12e81
Merged-In: I4163b2f9c6f80b4e639d9977ef7e2b444ab12e81