change persist.sys.usb.config=mtp

Should probably change this too since sdcard is now
recognized as mtp device. Dunno. Will see tomorrow.

Change-Id: Ie449d323e824bcba055bc195fe4da7912b62b126
Merge branch 'cm-11.0' of https://github.com/Mustaavalkosta/android_device_htc_ace into cd-4.4