DOC: option redispatch should mention persist options

DOC: option redispatch should mention persist options

"option redispatch" remains vague in which cases a session would persist;
let's mention "option persist" and "force-persist" as an example so folks
don't draw the conclusion that this may be default.

Should be backported to stable branches.

(cherry picked from commit 5926fb78233ab4ba95b07db3815ee62f5cbc5082)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 6d1a374721b2813a2ad61bf0e88e0e58a2a0c8b0)
Signed-off-by: Willy Tarreau <w@1wt.eu>