More canonical debug format for vmod_cache_req_body as suggested by fgs

lib/libvmod_std/vmod_std.c

@@ -237,5 +237,5 @@ vmod_cache_req_body(const struct vrt_ctx *ctx, VCL_BYTES size)
 	int result;
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	result = VRT_CacheReqBody(ctx, size);
-	VSLb(ctx->vsl, SLT_Debug,"VRT_CacheReqBody[size: %zu] result: %d", (size_t)size, result);
+	VSLb(ctx->vsl, SLT_Debug,"VRT_CacheReqBody(%zu): %d", (size_t)size, result);
 }