test-fuse.sh: make ls output locale independent

Call "ls" with LC_ALL set to "C".

(Otherwise it reports "total" for English, "insgesamt" for German;
other locales would be similar.)

Signed-off-by: Tim Riemenschneider <git@tim-riemenschneider.de>
[rlb@defaultvalue.org: adjust commit message]
Reviewed-by: Rob Browning <rlb@defaultvalue.org>
Tested-by: Rob Browning <rlb@defaultvalue.org>