BUG/MINOR: cli: fix server name output in "show fd"

BUG/MINOR: cli: fix server name output in "show fd"

A server name was displayed as <srv>/<proxy> instead of the reverse.
It only confuses diagnostics. This was introduced by commit 7a4a0ac71
("MINOR: cli: add a new "show fd" command") so this fix can be backport
down to 1.8.

(cherry picked from commit dfb34a8f87cacc1ced48f555ab74b6630ce4bb08)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit ab40792af6b81e45e632b5c14d396aba4efb4cde)
Signed-off-by: Willy Tarreau <w@1wt.eu>