Regression: wifi fails to connect directly after resume

[dronus]

If my Thinkpad T420s using Ubuntu 14.04.3 resumes from standby, it immediately tries to reconnect to my wifi, but is trying a long time without success until some timeout. It retrys then, successfully.

I can stop this manually by selecting disconnect and the network manually again, which leads to a successful connection.

dmesg states for the first unsucessful try:

[XXXXXXXXXX] wlan0: deauthenticating from XX:XX:XX:XX:XX:XX by local choice (Reason: 3=DEAUTH_LEAVING)

This worked well on Ubtuntu 12.04. However it take a little longer delay between wakeup and connect there if I remember right.