MINOR: contrib/prometheus-exporter: Split the PROMEX_FL_STATS_METRIC flag

PROMEX_FL_STATS_METRIC flag is splitted in 3 flags to easily identify the
processed entity type (frontend, backend or server). Thus, now we are using
PROMEX_FL_FRONT_METRIC, PROMEX_FL_BACK_METRIC or PROMEX_FL_SRV_METRIC. These
flags will be used to know if a metric is defined and must be exported for a
given entity type.
1 file changed