Fix editor crash on rotation when no default account exists

Persist the current primary account in the fragment. Normally a
default account has to be chosen before a new contact is added
but when adding a new contact from an account view, that account
is passed in through an intent extra and set as the primary for
the fragment. On rotation it's lost because reading the intent
extras only happens when saveState is null.
Also remove an unused constant.

Test: Followed repro steps in the bug and verified no crash
happens and the new contact is saved to the correct account.

Bug: 33691259
Change-Id: I12a86af907be7d11980349583fa6d44b3097de15