kvm tools: Set active console before running /bin/sh
This patch sets active console to the serial console before running the
shell. Doing so fixes two issues:
* Fix job control.
* Set all env vars.
The user visible issues are less warnings (no more of this:
sh: cannot set terminal process group (-1): Inappropriate ioctl for device
sh: no job control in this shell)
A working 'top', and a working ctrl-c.
Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Pekka Enberg <penberg@kernel.org>