ss: use compact output for undetected screen width

ss: use compact output for undetected screen width

This change fixes calculation of width in case user pipes the output.

SS output output works correctly when stdout is a terminal. When one
pipes the output, it tries to use 80 or 160 columns. That adds a
line-break if user has terminal width of 100 chars and output is of
the similar width. No width is assumed here.

To reproduce the issue, call
ss | less
and see every other line empty if your screen is between 80 and 160
columns wide.

This second version of the patch fixes screen_width being set to arbitrary
value.

Signed-off-by: Peter Junos <petoju@gmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>