Fix violations of H302:import only modules

Comment '# noqa' was missed in some files, led to pep8 warning.
And some modules imported non-module. This patch fixes them.
This is output of violation:
http://logs.openstack.org/77/60977/1/check/gate-oslo-incubator-pep8/4a00515/

Change-Id: Id79bca9820853ecd9f0660a855d7bb2fe42ec806