MINOR: actions: Export actions lookup functions

These functions will be useful to check if a keyword is already registered.
This will be needed by a next patch to fix a bug, and will need to be
backported.

(cherry picked from commit 7a71a6d9d262d7a0f7c3d208ab339d469958011d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
4 files changed