Scenario : Start instances using fixed network when possible
Scenario : Start instances using fixed network when possible

Uses the fixed_network_name option to select which network
to boot test instances on.  This allows Tempest to be run
in environments where there are multiple networks available.

Change-Id: I64ad6ce6bee3fe33537ac4f8d8d913856fe46554
Partial-Bug: #1250866

FujitsuEnablingSoftwareTechnologyGmbH/tempest,zsoltdudas/lis-tempest,varunarya10/tempest,masayukig/tempest,afaheem88/tempest,cisco-openstack/tempest,JioCloud/tempest,hpcloud-mon/tempest,rzarzynski/tempest,afaheem88/tempest,Lilywei123/tempest,flyingfish007/tempest,vedujoshi/os_tempest,bigswitch/tempest,rakeshmi/tempest,pandeyop/tempest,Mirantis/tempest,neerja28/Tempest,Tesora/tesora-tempest,jamielennox/tempest,NexusIS/tempest,redhat-cip/tempest,hayderimran7/tempest,JioCloud/tempest,LIS/lis-tempest,cloudbase/lis-tempest,varunarya10/tempest,vedujoshi/os_tempest,pczerkas/tempest,akash1808/tempest,openstack/tempest,Vaidyanath/tempest,rakeshmi/tempest,cloudbase/lis-tempest,akash1808/tempest,rzarzynski/tempest,tudorvio/tempest,xbezdick/tempest,izadorozhna/tempest,flyingfish007/tempest,CiscoSystems/tempest,manasi24/tempest,CiscoSystems/tempest,queria/my-tempest,bigswitch/tempest,ebagdasa/tempest,eggmaster/tempest,NexusIS/tempest,queria/my-tempest,cisco-openstack/tempest,ebagdasa/tempest,sebrandon1/tempest,manasi24/jiocloud-tempest-qatempest,roopali8/tempest,masayukig/tempest,redhat-cip/tempest,alinbalutoiu/tempest,izadorozhna/tempest,Vaidyanath/tempest,dkalashnik/tempest,yamt/tempest,sebrandon1/tempest,vedujoshi/tempest,Juraci/tempest,nunogt/tempest,Juraci/tempest,pczerkas/tempest,openstack/tempest,pandeyop/tempest,tudorvio/tempest,hpcloud-mon/tempest,danielmellado/tempest,xbezdick/tempest,jaspreetw/tempest,Lilywei123/tempest,FujitsuEnablingSoftwareTechnologyGmbH/tempest,jamielennox/tempest,neerja28/Tempest,Juniper/tempest,Mirantis/tempest,eggmaster/tempest,tonyli71/tempest,jaspreetw/tempest,vmahuli/tempest,nunogt/tempest,yamt/tempest,afaheem88/tempest_neutron,vmahuli/tempest,vedujoshi/tempest,danielmellado/tempest,alinbalutoiu/tempest,manasi24/tempest,manasi24/jiocloud-tempest-qatempest,tonyli71/tempest,afaheem88/tempest_neutron,roopali8/tempest,LIS/lis-tempest,hayderimran7/tempest,dkalashnik/tempest,Tesora/tesora-tempest,Juniper/tempest,zsoltdudas/lis-tempest