Fix minor error in extarq job
Fix minor error in extarq job

The patch fix the var need_job init value to False,
In some case, The None will cause some errors that
are not easy to be detected.

Change-Id: Ic4eac2fbc274fc5dfe9b2f4b796888b96bd78d0c
Story: 2007352
Task: 38932

openstack/nomad