BUG/MINOR: stats: fix compare of no-maint url suffix

BUG/MINOR: stats: fix compare of no-maint url suffix

Only the first 3 characters are compared for ';no-maint' suffix in
http_handle_stats. Fix it by doing a full match over the entire suffix.

As a side effect, the ';norefresh' suffix matched the inaccurate
comparison, so the maintenance servers were always hidden on the stats
page in this case.

no-maint suffix is present since commit
  3e320367014c742814ba494594cdb8340b1161f1
  MINOR: stats: also support a "no-maint" show stat modifier

It should be backported up to 2.3.

This fixes github issue #1147.

(cherry picked from commit 91e55ea3f3f6277d91c0fd85ea924ea0e444f7f3)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>