btrfs: factor btrfs_read_roots() out of open_ctree()
btrfs: factor btrfs_read_roots() out of open_ctree()

Also, remove the two local variables create_uuid_tree
and check_uuid_tree; we can use the existence of
the uuid root and/or the RESCAN_UUID_TREE flag to
determine what action to take.

Signed-off-by: Eric Sandeen <d55521028c14e0f378be5444e4ea388161c0d7e7@redhat.com>
Signed-off-by: David Sterba <a2ce9d316ca04d17b520237d2846a218b8284e52@suse.cz>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs