dvc tries to launch updater using asv script

[efiop]

In every run you can see:

               2020-07-03 23:24:19,549 DEBUG: Trying to spawn '['/home/efiop/git/dvc-bench/envs/76391772e92136ec87b9940d70226329/bin/python', '
/home/efiop/.pyenv/versions/3.8.3/envs/dvc-3.8.3/lib/python3.8/site-packages/asv/benchmark.py', 'daemon', '-q', 'updater']'
               2020-07-03 23:24:19,550 DEBUG: Spawned '['/home/efiop/git/dvc-bench/envs/76391772e92136ec87b9940d70226329/bin/python', '/home/ef
iop/.pyenv/versions/3.8.3/envs/dvc-3.8.3/lib/python3.8/site-packages/asv/benchmark.py', 'daemon', '-q', 'updater']'
               Unknown mode daemon

we clearly need to take more care on dvc-side, but a good enough workaround is to set CI or DVC_TEST env var to make dvc skip launching the updater.