test-ls.sh: get the symlink mode from the host ls; test for subcmd failure.
test-ls.sh: get the symlink mode from the host ls; test for subcmd failure.

This should fix a failure on OS X where symlinks don't have a
"rwxrwxrwx" mode like they do on Linux.

Thanks to Sashka Will <will.sashka@gmail.com> for the report.

Signed-off-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

jbaber/bup,ToxicFrog/bup,ToxicFrog/bup,tjanez/bup,pombredanne/bup,mhoeher/bup,mhoeher/bup,jbaber/bup,mhoeher/bup,mhoeher/bup,gevaerts/bup,pombredanne/bup,tjanez/bup,pombredanne/bup,tjanez/bup,jbaber/bup,mhoeher/bup,ToxicFrog/bup,mhoeher/bup,tjanez/bup,jbaber/bup,ToxicFrog/bup,pombredanne/bup,jbaber/bup,pombredanne/bup,gevaerts/bup,jbaber/bup,gevaerts/bup,tjanez/bup,gevaerts/bup,pombredanne/bup,gevaerts/bup,tjanez/bup,ToxicFrog/bup