Passing of environment variables doesn't work

[zemlanin]

Neither -e nor VAGGAENV_* pass env vars through (but -E does)

# vagga.yaml
containers:
  c:
    setup: [!Alpine v3.5]

$ pip3 install --upgrade git+http://github.com/tailhook/vagga-box
# ...

$ vagga --version
v0.8.1-12-gc0c3378

$ X=1 vagga -eX _run c env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
X=
TERM=screen-256color

$ VAGGAENV_X=1 vagga _run c env
TERM=screen-256color
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

$ vagga -E X=1 _run c env
TERM=screen-256color
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
X=1