Replace some utils.bool_from_str with strutils

Instead of using novaclient.utils' bool_from_str, use bool_from_string
from the oslo incubating strutils

Notes:
 0. utils.bool_from_str was strict, only accepted a small set of
    values, while strutils.bool_from_string is not strict by default,
    anything not true is false
 1. bool_from_string accepts on/off, which bool_from_str did not

Change-Id: I04744844b55697819289def081d3c9117ed0713f
Merge "Replace some utils.bool_from_str with strutils"