With the test-list option, refstack-client will first normalize the
user input test list to the test list from the currently installed
Tempest. There seems to be some non RefStack updates in the recent
releases that "testr list-tests" would now require a valid
tempest.conf for test listing. The path of the tempest.conf file
is determined by the .tempest/tempest/config.py module. If a
tempest.conf file is not found, then the failsafe file is used,
namely "/etc/tempest/tempest.conf" which does not exist in
refstack-client.
This patch initialzes the tempest conf related environment variables
with the user passes in information before starting the test run.
Closes-Bug: #1516458
Change-Id: Ic2cdbdcdf575e23cb0fc59c5478ceda5807c06fb
1d392df77f