[pool] Fix check for reopenable pooled connections

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/pool.h

 	/* A connection is reopenable if it has been recycled but is
 	 * not yet known to be alive.
 	 */
-	return ( ( pool->flags & POOL_RECYCLED ) &
+	return ( ( pool->flags & POOL_RECYCLED ) &&
 		 ( ! ( pool->flags & POOL_ALIVE ) ) );
 }