py3: Fix list_entries for netlink_lib
py3: Fix list_entries for netlink_lib

As privsep communicates with main process via socket, data passed
through this socket must be string type in Python 3. This patch converts
bytes to string, then privsep works correctly.

Change-Id: I6838d13b5acc32e939fba3c9abfea7cd483e971b
Closes-bug: #1771410

mahak/neutron,huntxu/neutron,mahak/neutron,noironetworks/neutron,openstack/neutron,huntxu/neutron,mahak/neutron,noironetworks/neutron,openstack/neutron,openstack/neutron