Reload allowed networks from db after restore content.

Since the allowed networks in db has changed after restoring the 2g
settings, reload based on the db again.

Bug: 314734614
Test: atest com.android.providers.telephony.TelephonyProviderTest
Test: tested manually with Pixel7, backup, factory reset and restored.
Test: basic telephony test call/data/networksetting
Change-Id: I93118985e9d8603c67b4d87ddb93bc72fb76f286