WifiConfigManager: Explcitly set the disable reason for new networks

New networks added start out with network selection "status" marked disabled,
also set the "disable reason" explicitly to be consistent.

Note: This does not fix any issues other than the discrepancy noticed
between "status" and "disable reason" in network selection status.

Bug: 79750205
Test: Unit tests
Change-Id: I4be4e3d1719bc34b62e527294e0d59b3dd1b1627
2 files changed