webos-image-devel: add htop package

enable htop in webos test package group
htop is an interactive system-monitor process-viewer.

[GF-4196] Integrate tool for understanding the CPU cores usage

Open-webOS-DCO-1.0-Signed-off-by: Seungkyun Kim <seungkyun.kim@lge.com>

Change-Id: Ic131ac8bcc1660f8ae896816b3f74fa741b39d1b
Reviewed-on: https://g2g.palm.com/2050
Reviewed-by: Seungkyun Kim <seungkyun.kim@lge.com>
Tested-by: Seungkyun Kim <seungkyun.kim@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Lokesh Kumar Goel <lokeshkumar.goel@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>