Get follwing error when running tox -edocs

doc/bifrost.rst:91: D001 Line too long
doc/manila-hnas-guide.rst:28: D000 Title underline too short.
doc/manila-hnas-guide.rst:28: D000 Title underline too short.
doc/networking-guide.rst:93: D000 Title underline too short.
doc/networking-guide.rst:93: D000 Title underline too short.
doc/multinode.rst:14: D001 Line too long
doc/quickstart.rst:474: D001 Line too long
doc/vagrant-dev-env.rst:129: D001 Line too long

Change-Id: I88090487a4710547224361d29aaf8371f8340c28