Properly set up environment
Properly set up environment

More awesomeness by @JessThrysoee

Now using su to;
- Automatically log in to the default shell of the container
- Set up the right environment variables (e.g. $PATH, $HOME)
- No longer requiring to *detect* the default shell

Yong-Lee/nsenter,dalanlan/nsenter,BWITS/nsenter,dalanlan/nsenter,aaam/nsenter,jasonchaffee/nsenter,aaam/nsenter,BWITS/nsenter,oouyang/nsenter,Yong-Lee/nsenter,jpetazzo/nsenter,jpetazzo/nsenter,oouyang/nsenter,ccortezb/nsenter,jasonchaffee/nsenter,ccortezb/nsenter