Couple of fixes to tempest/auth
Couple of fixes to tempest/auth

Basically if you don't pass a header, the method header was None and later
when you try to assign a value to it's copy in _decorate_request method you
try to assign a value to a NoneType. Fixed the issue changing the copy to
fallback and provide an empty dict in case headers are None (The assign occours
in line 181).

The second fix is related to the base_url method in Keystone v3 provider. We
test the size of the filtered catalog matches and if equals to zero we need to
assign it to the first endpoint in the service catalog instead of the filtered
catalog itself (which has length zero, so impossible).

Related to bp unit-tests

Change-Id: I9f11ddcb6f34c0161cb338a1956cefc52e990af2

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