btrfs: remove remapped block groups from the free-space-tree

btrfs: remove remapped block groups from the free-space-tree

No new allocations can be done from block groups that have the REMAPPED
flag set, so there's no value in their having entries in the free-space
tree.

Prevent a search through the free-space tree being scheduled for such a
block group, and prevent any additions to the in-memory free-space tree.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Mark Harmstone <mark@harmstone.com>
Signed-off-by: David Sterba <dsterba@suse.com>