BUG/MINOR: mux-h2: fix expression when detecting excess of CONTINUATION frames

BUG/MINOR: mux-h2: fix expression when detecting excess of CONTINUATION frames

Latest commit f0eca8fe7 ("MINOR: mux-h2/glitches: add a description to
the H2 glitches") misplaced the optional glitch description field, with
it appearing at the end of the if () condition and always reporting
an excess of CONTINUATION frames from the first exceeding one.

This needs to be backported along with that commit once it gets backported.

(cherry picked from commit cb21db04c748a77122c118a3d526fdc058ca564f)
Signed-off-by: Willy Tarreau <w@1wt.eu>