Replace deprecated library function os.popen() with subprocess
Replace deprecated library function os.popen() with subprocess

os.popen() is deprecated since version 2.6. Resolved with use of
subprocess module.

Change-Id: If3be398196688c9634cb12bfd96daac71f0bf42d
Closes-Bug: #1529836

openstack/networking-powervm,openstack/networking-powervm,stackforge/neutron-powervm,stackforge/neutron-powervm