btrfs: return an error from btrfs_record_root_in_trans

We can create a reloc root when we record the root in the trans, which
can fail for all sorts of different reasons.  Propagate this error up
the chain of callers.  Future patches will fix the callers of
btrfs_record_root_in_trans() to handle the error.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>