services/device/devicex: mkdir -p
services/device/devicex: mkdir -p

When creating the debian package for deviced, it is helpful for the
devmgr directory to be created as part of devicex rather than as
part of the postinstall script because devicex runs as the devmgr user.

Change-Id: Icff6d8836da08a19fb3f1607b43d10932801e2fc

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref