Enable benchHandler on "/bench/" in addition of "/bench"

[mvertes]

Adding the trailing slash allows to trigger the bench handler for
performance measurements in situations where a trailing slash
character '/' is added to the request.

For example, in traefik addPrefix middleware, if you specify a
"/bench" prefix, a request on "http://localhost" will be transformed
from "GET /" to "GET /bench/" with no way to remove the trailing
'/' (at least without adding another rewrite rule, which would
modify measurements).