test-ls: discover socket mode like symlink mode
test-ls: discover socket mode like symlink mode

This addresses the single failed test under Cygwin. Tested on both a
new Cygwin64 installation and (Fedora) Linux.

On Cygwin64 the full mode is "srw-------" rather than "srwx------".

Signed-off-by: Paul Kronenwetter <83dc2024482079750b989ee5e129da5b9fd83320@gmail.com>
[1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org: adjust commit message]
Reviewed-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>
Tested-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

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