dns_cache: optimize timer wheel for DNS cache

src/lib/timer_wheel.c

@@ -27,7 +27,7 @@
 
 #include "timer_wheel.h"
 
-#define TVR_BITS 8
+#define TVR_BITS 10
 #define TVN_BITS 6
 #define TVR_SIZE (1 << TVR_BITS)
 #define TVN_SIZE (1 << TVN_BITS)
@@ -416,4 +416,4 @@ errout2:
 	free(base);
 errout:
 	return NULL;
-}
+}