Add pep8 job to Jenkins for python-ipmi.

* ,,,/jenkins_job_builder/config/projects.yaml: Add python-jobs
job group to the python-ipmi project to create a gate-python-ipmi-pep8
job on the Jenkins server. The zuul layout is already attempting to run
this job.

Change-Id: I49f93cc885d25bbe20dc0d350af897451e31adf5