Extend default setenv instead of replacing it in tox.ini
Extend default setenv instead of replacing it in tox.ini

Some tox jobs[1] define their own setenv without extending/referencing
default setenv, it disallows to define environment variables shared by
all jobs. This change updates previous jobs[1] in order to extend
instead of replacing default setenv and enable global environement
variables (used in daughter change).

One remark, this change sets VIRTUAL_ENV environment variable in updated
jobs[1] but it has no effect on them.

[1] (dsvm-)functional, (dsvm-)fullstack and api jobs

Closes-Bug: #1468059
Change-Id: I99184f7375571fb8569a24ba04ae267108f5da08

dims/neutron,MaximNevrov/neutron,dhanunjaya/neutron,takeshineshiro/neutron,watonyweng/neutron,barnsnake351/neutron,yanheven/neutron,SamYaple/neutron,JianyuWang/neutron,dhanunjaya/neutron,openstack/neutron,eayunstack/neutron,adelina-t/neutron,sasukeh/neutron,javaos74/neutron,sasukeh/neutron,JianyuWang/neutron,swdream/neutron,skyddv/neutron,suneeth51/neutron,wolverineav/neutron,eonpatapon/neutron,suneeth51/neutron,mahak/neutron,cloudbase/neutron,bigswitch/neutron,cisco-openstack/neutron,eayunstack/neutron,mattt416/neutron,dims/neutron,igor-toga/local-snat,mandeepdhami/neutron,SamYaple/neutron,bigswitch/neutron,openstack/neutron,asgard-lab/neutron,mandeepdhami/neutron,shahbazn/neutron,jumpojoy/neutron,javaos74/neutron,barnsnake351/neutron,glove747/liberty-neutron,sebrandon1/neutron,MaximNevrov/neutron,swdream/neutron,mmnelemane/neutron,adelina-t/neutron,vivekanand1101/neutron,jacknjzhou/neutron,silenci/neutron,mahak/neutron,vivekanand1101/neutron,neoareslinux/neutron,mmnelemane/neutron,apporc/neutron,paninetworks/neutron,cisco-openstack/neutron,cloudbase/neutron,yanheven/neutron,asgard-lab/neutron,igor-toga/local-snat,mahak/neutron,skyddv/neutron,jumpojoy/neutron,huntxu/neutron,sebrandon1/neutron,eonpatapon/neutron,noironetworks/neutron,noironetworks/neutron,chitr/neutron,takeshineshiro/neutron,silenci/neutron,huntxu/neutron,wenhuizhang/neutron,neoareslinux/neutron,apporc/neutron,wolverineav/neutron,glove747/liberty-neutron,openstack/neutron,watonyweng/neutron,wenhuizhang/neutron,paninetworks/neutron,shahbazn/neutron,klmitch/neutron,jacknjzhou/neutron,mattt416/neutron,klmitch/neutron,chitr/neutron