vinyl: implement vy_quota_wait using vy_quota_use

So that there's a single place where we can wait for quota. It should
make it easier to implement quota throttling.

src/box/vy_quota.c

@@ -227,10 +227,3 @@ vy_quota_adjust(struct vy_quota *q, size_t reserved, size_t used)
 	if (reserved < used)
 		vy_quota_force_use(q, used - reserved);
 }
-
-void
-vy_quota_wait(struct vy_quota *q)
-{
-	while (q->used > q->limit)
-		fiber_cond_wait(&q->cond);
-}

src/box/vy_quota.h

@@ -196,8 +196,11 @@ vy_quota_adjust(struct vy_quota *q, size_t reserved, size_t used);
 /**
  * Block the caller until the quota is not exceeded.
  */
-void
-vy_quota_wait(struct vy_quota *q);
+static inline void
+vy_quota_wait(struct vy_quota *q)
+{
+	vy_quota_use(q, 0, TIMEOUT_INFINITY);
+}
 
 #if defined(__cplusplus)
 } /* extern "C" */