BUG/MINOR: pools: use %u not %d to report pool stats in "show pools"

In dump_pools_to_trash() we happen to use %d to display unsigned ints!

This has probably been there since "show pools" was introduced so this
fix must be backported to all versions. The impact is negligible since
no pool uses 2 billion entries. It could possibly affect the report of
failed allocation counts but in this case there's a bigger problem to
solved!
diff --git a/src/memory.c b/src/memory.c
index 551ca83..5db2c35 100644
--- a/src/memory.c
+++ b/src/memory.c
@@ -486,7 +486,7 @@
 #ifndef CONFIG_HAP_LOCKLESS_POOLS
 		HA_SPIN_LOCK(POOL_LOCK, &entry->lock);
 #endif
-		chunk_appendf(&trash, "  - Pool %s (%d bytes) : %d allocated (%u bytes), %d used, %d failures, %d users, @%p=%02d%s\n",
+		chunk_appendf(&trash, "  - Pool %s (%u bytes) : %u allocated (%u bytes), %u used, %u failures, %u users, @%p=%02d%s\n",
 			 entry->name, entry->size, entry->allocated,
 		         entry->size * entry->allocated, entry->used, entry->failed,
 			 entry->users, entry, (int)pool_get_index(entry),