Use carrier config to define network validation cache ttl.

Also add a flag to control when to report validation pass upon
validated network cache hit (immediately upon request or wait until
network becomes available).

Bug: 140070796 148611362
Test: unittest
Change-Id: I1377f2d7b249b62d6aac6b581dc3ba4908527fc9
Merged-In: I1377f2d7b249b62d6aac6b581dc3ba4908527fc9
2 files changed