Remove "updatecmds" feature.

This feature is very old and hasn't been used in many releases.  In
addition, it was never taught about multi-user layouts, and it would
be incredibly hard to maintain in the new FBE world where CE keys
may not appear until several reboots after an OTA.

Bug: 26854442
Change-Id: Ibd8660e2a727469cd5ae41dab5e1014a9cfb6748