[Settings] Connected carrier should not be forbidden ones

Manual network selection UI tried to display connected carrier as
initial list prior to the initial response from network scan.
However, the detection of connected carrier could be incorrect.

Before having an architectural change for this part, adding a piece of
code to avoid from displaying carriers which should be avoided.

Bug: 165158590
Test: local
Change-Id: If9c0804c706dd77a1c690555b245425dfeaf1fa9