This NetworkManager's "dispatch script" forced yum to check your cache when establishing a new network connection. Note that currently there is no verification of previous data, so if the WiFi connection passes from top to bottom, or if you suspend / resume often yum will check your cache many times.

/etc/NetworkManager/dispatcher.d/yum-NetworkManager-dispatcher is the script for NetworkManager, if you have any other action combined with the cache verification, you could edit this file freely.