Fixed incorrect phone number from inactive subscription

When the subscription inactive, SubscriptionManager.getPhoneNumber()
returns incorrect phone number from the active subscription.

Fixed by using getSlotIndex which would not give default phone id
when subscription is inactive.

Fix: 286124301
Test: atest SubscriptionManagerServiceTest
Test: Basic telephony functionality tests
Test: eSIM transfer and confirmed the phone number was displayed properly (b/293623063#comment6)
Change-Id: I071fdb62fcb3a754dfaf32e7198cdfb6f762eaac