MINOR: action: Use a generic function to check validity of an action rule list

MINOR: action: Use a generic function to check validity of an action rule list

The check_action_rules() function is now used to check the validity of an
action rule list. It is used from check_config_validity() function to check
L5/6/7 rulesets.

(cherry picked from commit 42c6cf950111736327863de5e82036a1d51deb04)
[cf: This patch is in fact a fix because the "tcp-resonse content" ruleset
     was not fully configured. It was ignored during Post-parsing
     stage. This patch should fix a bug reported in #1263 by @ HiggTh. It
     must be backported in all stable versions.]
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>