Rename pep8 to linters test
Rename pep8 to linters test

The pep8 tests does more than calling pep8, rename it to use the new
linters standard job for all lint like jobs.

Change-Id: I027795072ce6fef13026099c3834a0d33ca7f7f7
Depends-On: I7cf4766642dc3e7d7652e6d26ab2f14f9fcd7861

openstack/openstack-doc-tools,openstack/openstack-doc-tools