Revert an accidental error modification of config item help message
Revert an accidental error modification of config item help message

The help message of config.compute.fixed_network_name is changed in
Ied68c0326cf891a4e6eb3db51dc5f43241e4b8d2 accidiently which is unwanted,
so this is to revert it.
Besides, this is to remove some unwanted words.

Change-Id: Ia4979772faf33d90f9544c510f4c421c4fa0097f

cisco-openstack/tempest,Juniper/tempest,vedujoshi/tempest,Juniper/tempest,openstack/tempest,cisco-openstack/tempest,masayukig/tempest,Tesora/tesora-tempest,sebrandon1/tempest,Tesora/tesora-tempest,openstack/tempest,sebrandon1/tempest,masayukig/tempest,vedujoshi/tempest