[android] fix IllegalStateException when creating attachments

Injecting the non-singleton AttachmentCreator keeps an instance around
that gets re-used with a different ViewModel.
When backing out without sending or cancelling the attachments,
we don't reset the state which leads us into an illegal state.
1 job for 1647-illegal-state in 12 minutes and 22 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #4222
test

00:12:22