restore: Split output directory and btrfs-local path search_dir() parameters

restore: Split output directory and btrfs-local path search_dir() parameters

search_dir() recurses down the btrfs tree, and used to take the output
path for every item (i.e. in the running system, output root directory
concatenated with btrfs-local pathname) passed as the only path
parameter. Moving the output root directory to a separate parameter
and passing the btrfs-local pathname for each file and directory
separately allows easy filtering based on the btrfs-local pathname.

Signed-off-by: Peter Stuge <peter@stuge.se>
Signed-off-by: Josef Bacik <josef@redhat.com>