Change the multipath hint default to 0.

It was set to 3 (handover+reliability) during the development
cycle, but should not be set to a nonzero value on user devices
until the returned value takes into account the amount of
non-default network data usage.

Bug: 34630278
Test: marlin builds and boots
Test: ConnectivityServiceTest passes
Change-Id: I2b09a6e09c497886862cbaaaf3b283dedfbfa94c