Don't match network requests to legacy API requests.

Currently, we look at network requests that are created by the
current requestNetwork API to see if they look like requests
that could have been created using the legacy
startUsingNetworkFeature API.

This causes those networks to be added to LegacyTypeTracker,
and so cause CONNECTIVITY_ACTION broadcasts, be accessible
using getNetworkInfo(int type), etc. This was done in the L
timeframe so that apps could request networks using the
then-new requestNetwork APIs and still use them using legacy
APIs such as requestRouteToHost.

However, the resulting CONNECTIVITY_ACTION broadcasts are
expensive. requestRouteToHost has been deprecated since L, and
mixing the old and new APIs was never recommended, so it's time
to delete this hack.

Bug: 22513439
Bug: 23350688
Bug: 25295964
Change-Id: Id867058446e5ee44396743d126d26fa57da0c990