ss: fix output of MD5 signature keys configured on TCP sockets

ss: fix output of MD5 signature keys configured on TCP sockets

da9cc6ab introduced printing of MD5 signature keys when found.
But when changing printf() to out() calls with 90351722,
the implicit printf call in print_escape_buf() was overlooked.
That results in a funny output in the first line:
"<all-your-tcp-signature-keys-concatenated>State"
and ambiguity as to which of those bytes belong to which socket.

Add a static void out_escape_buf() immediately before we use it.

da9cc6ab (ss: print MD5 signature keys configured on TCP sockets, 2017-10-06)
90351722 (ss: Replace printf() calls for "main" output by calls to helper, 2017-12-12)

Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>