Description of problem:
the oslo_rootwrap wrapper.py component checks for the existence of /dev/log.  But if Journald/rsyslog is not running, /dev/log does not exist.  This causes cold migrations, which use oslo_rootwrap, to fail.

Version-Release number of selected component (if applicable):


How reproducible:
Every time

Steps to Reproduce:
1. Stop journald and rsyslog, and verify /dev/log is not present
2. Attempt to perform a cold migration of a host 
3. Test that ssh communications is working with the nova_migrate user:  
ssh -i /etc/nova/migration/identity nova_migration.ip.address  touch /var/lib/nova/instances/test

Actual results:
cold migration will fail.  the ssh test will fail with the following error:

Traceback (most recent call last):
  File "/usr/bin/nova-rootwrap", line 10, in <module>
    sys.exit(main())
  File "/usr/lib/python2.7/site-packages/oslo_rootwrap/cmd.py", line 89, in main
    config.syslog_log_level)
  File "/usr/lib/python2.7/site-packages/oslo_rootwrap/wrapper.py", line 101, in setup_syslog
    facility=facility)
  File "/usr/lib64/python2.7/logging/handlers.py", line 761, in __init__
    self._connect_unixsocket(address)
  File "/usr/lib64/python2.7/logging/handlers.py", line 789, in _connect_unixsocket
    self.socket.connect(address)
  File "/usr/lib64/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
socket.error: [Errno 2] No such file or directory

Expected results:
Cold migration should work.  The ssh test should complete successfully.

Additional info:

There is an upstream fix for this, which we would like backported to OSP10.