Go to /system/customize/ACC/default.xml and edit this two lines:
<item type="boolean" name="isHtcStyleRecentApp">true</item>
<item type="boolean" name="support_HtcStyleRecentApp">true</item>
They are about at lines 413 and 434.
Edit the file with Notepad++ on your computer, replace "true" by "false" then copy/paste the file and set the correct permissions like the original file, reboot and you're good
You can also edit the file directly from your phone with a file explorer, save and reboot.
Or send your default.xml file and I'll edit it for you.
-Black Nexus 5 32 Go
-Black LG G2 16 Go
-HTC Desire HD/HTC Sensation/Samsung Galaxy Nexus/Samsung Galaxy SIII/LG Nexus 4/HTC One...
Unfortunately smartphone user doesn't mean smart user....