MINOR: contrib/prometheus-exporter: avoid connection close header

it does not seem to have a reason to close connections after each
request; reflect that in tests by doing all requests within the same
client.

Signed-off-by: William Dauchy <wdauchy@gmail.com>
(cherry picked from commit 1704efee89c9a0d430e63e7a9b54e97644d27a2a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
2 files changed