Increase precision in box.slab.info()

Use two decimal digits in fractional part of quota_used_ratio and
arena_used_ratio.

Closes #2082

src/box/lua/slab.c

@@ -140,7 +140,7 @@ lbox_slab_info(struct lua_State *L)
 
 	ratio = 100 * ((double) totals.used
 		/ ((double) totals.total + 0.0001));
-	snprintf(ratio_buf, sizeof(ratio_buf), "%0.1lf%%", ratio);
+	snprintf(ratio_buf, sizeof(ratio_buf), "%0.2lf%%", ratio);
 
 	/*
 	 * Fragmentation factor for tuples. Don't account indexes,
@@ -187,7 +187,7 @@ lbox_slab_info(struct lua_State *L)
 	 */
 	ratio = 100 * ((double) quota_used(memtx_quota) /
 		 ((double) quota_total(memtx_quota) + 0.0001));
-	snprintf(ratio_buf, sizeof(ratio_buf), "%0.1lf%%", ratio);
+	snprintf(ratio_buf, sizeof(ratio_buf), "%0.2lf%%", ratio);
 
 	lua_pushstring(L, "arena_used_ratio");
 	lua_pushstring(L, ratio_buf);