bootctl: fix reconnect logic

Instead of just logging an error message, let's try reonnecting to the
bootctl service if our death recipient is invoked. We should also
reconnect our death recipient here.

If binder is killed, our death recipient is automatically unlinked.

Bug: 369289491
Test: kill bootctl service on CVD. Apply OTA
Change-Id: I914643baaf1fa6fe1e192517a2e43e07ee749b70