btrfs: enhance transaction abort infrastructure

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

diff --cc fs/btrfs/ctree.h
Simple merge

diff --cc fs/btrfs/disk-io.c
Simple merge

diff --cc fs/btrfs/disk-io.h
Simple merge

diff --cc fs/btrfs/relocation.c
Simple merge

diff --cc fs/btrfs/scrub.c
Simple merge

diff --cc fs/btrfs/super.c
Simple merge

diff --cc fs/btrfs/transaction.c
Simple merge

diff --cc fs/btrfs/transaction.h
Simple merge