Fix some issues with restoring old backups.

There's a bug where if you restore a database with a different column
definition order than a new install, then column indexes in cursors
could be wrong. Closing and re-opening the database fixes this.

I also removed a reference to a possibly-closed database we were holding
onto in LiveRecipient.

app/src/main/java/org/thoughtcrime/securesms/database/SignalDatabase.kt

@@ -237,6 +237,9 @@ open class SignalDatabase(private val context: Application, databaseSecret: Data
         instance!!.rawWritableDatabase.execSQL("DROP TABLE IF EXISTS job_spec")
         instance!!.rawWritableDatabase.execSQL("DROP TABLE IF EXISTS constraint_spec")
         instance!!.rawWritableDatabase.execSQL("DROP TABLE IF EXISTS dependency_spec")
+
+        instance!!.rawWritableDatabase.close()
+        triggerDatabaseAccess()
       }
     }