Fix Calls/SMS default SIM selector

In cases where a SIM is initially disabled, even after you turn it on
the ListPreference's for selecting the default SIM for Calls and SMS
weren't working because the preference change listener wasn't getting
registered. This CL fixes that for these controllers by always
registering a change listener whenever we make the preference visible.

Fixes: 134472294
Bug: 135142209
Test: make RunSettingsRoboTests
Change-Id: Ia9362b7f26309bdbd6c5e8140fb606b28e2b34d8