[PATCH][DOC] fix ignore-persist/force-persist documentation

Shame on me, I didn't correctly document the "ignore-persist" statement (convinced I used it like this in my tests, which is not the case at all...) This fixes the doc and updates the proxy keyword matrix to add "force-persist".

-- 
Cyril Bonté



text/x-patch attachment: haproxy-1.4.4-persist-fix-doc.diff