ratelimit: add ratelimit_configured() helper

This helper alone doesn't make too much sense, but it's preparatory work
for #17274, and I guess it can't hurt to land it early, it does make the
ratelimit code a tiny bit prettier after all.

src/basic/ratelimit.c

@@ -13,7 +13,7 @@ bool ratelimit_below(RateLimit *r) {
 
         assert(r);
 
-        if (r->interval <= 0 || r->burst <= 0)
+        if (!ratelimit_configured(r))
                 return true;
 
         ts = now(CLOCK_MONOTONIC);

src/basic/ratelimit.h

@@ -17,4 +17,8 @@ static inline void ratelimit_reset(RateLimit *rl) {
         rl->num = rl->begin = 0;
 }
 
+static inline bool ratelimit_configured(RateLimit *rl) {
+        return rl->interval > 0 && rl->burst > 0;
+}
+
 bool ratelimit_below(RateLimit *r);