ignore build directory for pep8
ignore build directory for pep8

this mirrors the excludes from nova.

Change-Id: I0ca5f02918842fc708c704fcf2845936dc1c5965

FedericoRessi/networking-odl,CiscoSystems/networking-odl,schoksey/networking-odl,FedericoRessi/networking-odl,flavio-fernandes/networking-odl,schoksey/networking-odl,openstack/networking-odl,openstack/networking-odl,openstack/networking-odl,mestery/x-stackforge-odl,flavio-fernandes/networking-odl,CiscoSystems/networking-odl