ss: Actually print left delimiter for columns

ss: Actually print left delimiter for columns

While rendering columns, we use a local variable to keep track of the
field currently being printed, without touching current_field, which is
used for buffering.

Use the right pointer to access the left delimiter for the current column,
instead of always printing the left delimiter for the last buffered field,
which is usually an empty string.

This fixes an issue especially visible on narrow terminals, where some
columns might be displayed without separation.

Reported-by: YoyPa <yoann.p.public@gmail.com>
Fixes: 691bd854bf4a ("ss: Buffer raw fields first, then render them as a table")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Tested-by: YoyPa <yoann.p.public@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>