BUG/MEDIUM: checks: fix health check regression causing them to depend on declaration...

BUG/MEDIUM: checks: fix health check regression causing them to depend on declaration order

Since commit 4a74143 (MEDIUM: Paramatise functions over the check of a
server), the check type is inherited from the current proxy's check type
at the moment where the server is declared instead of when reviewing
server configs. This causes an issue where a health check is disabled
when the server is declared before the checks. In fact the server will
inherit the last known check type declared before the "server" line :

  backend foo
        # this server is not checked at all
        server s1 1.1.1.1:80 check
        option tcpchk
        # this server is tcp-checked :
        server s2 1.1.1.2:80 check
        option httpchk
        # this server is http-checked :
        server s3 1.1.1.3:80 check

The fix consists in assigning the check type during the config review
phase where the config is stable. No backport is nedeed.