Explicitly pass old score to updateCapabilities

This allows simplification of getCurrentScore function in
NetworkAgentInfo and its return value to depend on everValidated and
lastValidated.

Bug: 31075769
Change-Id: I0b3c85e3a61b006733e900e0a231424878317476
(cherry picked from commit f15b2824b6f954e3a8b039a0836530f571d663d0)
2 files changed