packagegroup-webos-test: Add iftop

- The iftop is a network monitoring tool

[GF-4197] Integrate tools to measure network performance for wired/wireless connection

Open-webOS-DCO-1.0-Signed-off-by: Sangwoo Kang <sangwoo82.kang@lge.com>

Change-Id: I3cbf84bedf9678fb4f0d54f8063acc8966b16740
Reviewed-on: https://g2g.palm.com/2062
Reviewed-by: Build Verification
Reviewed-by: Sangwoo Kang <sangwoo82.kang@lge.com>
Tested-by: Sangwoo Kang <sangwoo82.kang@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>