- remove load_tablet_metadata(), instead we add wake_up_load_balancer flag
to update_tablet_metadata(), it reduces number of public functions and
also serves as a comment (removed comment with very similar meaning)
- reimplement the code to not use mutate_token_metadata(), this way
it's more readable and it's also needed as we'll split
update_tablet_metadata() in following commits so that we can have
subroutine which doesn't yield (for ensuring atomicity)
1c8fd3a65d