[PATCH]: Check for duplicated conflicting proxies

[PATCH]: Check for duplicated conflicting proxies

Currently haproxy accepts a config with duplicated proxies
(listen/fronted/backed/ruleset). This patch fix this, so the application
will complain when there is an error.

With this modification it is still possible to use the same name for two
proxies (for example frontend&backend) as long there is no conflict:

                 listen backend frontend ruleset
listen             -      -       -        -
backend            -      -       OK       -
frontend           -      OK      -        -
ruleset            -      -       -        -

Best regards,

 				Krzysztof Oledzki
(cherry picked from commit 365d1cd84c5e44129a706629815f2721277c125f)