usertools: fix CPU layout with python 3

These differences in Python 3 were causing errors:
- xrange is replaced by range
- dict values are a view (instead of list)
- has_key is removed

Fixes: deb87e6777c0 ("usertools: use sysfs for CPU layout")
Fixes: 63985c5f104e ("usertools: fix CPU layout for more than 2 threads")

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Gowrishankar Muthukrishnan <gowrishankar.m@linux.vnet.ibm.com>