set the monitor process title to something useful

set the monitor process title to something useful

Instead of having a parent process that's called whatever the caller of the
library is called, we instead set it to "[lxc monitor] <lxcpath> <container>"

Closes #180

v2: check for null in tok for loop, only truncate environment when necessary

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>