Btrfs-progs: keep track of transid failures and fix them if possible

Btrfs-progs: keep track of transid failures and fix them if possible

A user was reporting an issue with bad transid errors on his blocks.  The thing
is that btrfs-progs will ignore transid failures for things like restore and
fsck so we can do a best effort to fix a users file system.  So fsck can put
together a coherent view of the file system with stale blocks.  So if everything
else is ok in the mind of fsck then we can recow these blocks to fix the
generation and the user can get their file system back.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>