Fix : Reconnection not triggered when APN changed

When APN is changed, connections whose ApnSetting change will be cleaned
up. However, as ApnSetting#equals doesn't check mmsPort, username and
password, connection will not be cleaned up even if user changes them.
To fix the issue, add logic to check them and also introduced test case
to prevent same failure in the future.

Bug: 30207789
Test: Telephony unit test
Change-Id: I4ac75ebac1755a42c4e88da60b059874ea9f693c