btrfs: pass fs_info to (more) routines that are only called with extent_root

Outside of interactions with qgroups, the roots passed in extent-tree.c
are usually passed to ensure that we don't do refcounts on log trees or
to get the allocation profile for an allocation request.  Otherwise, it
operates on the extent root.  This patch converts some more routines in
extent-tree.c that are always called with the extent root to accept
an fs_info instead.

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