Install iftop and sockstat on dev servers

Summary:
iftop and sockstat are network utilities to better visualize the traffic.

sockstat is shipped with FreeBSD base OS, and a Linux-compatible clone
is available for Debian family.

Test Plan: Tested on Eglide and Ysul

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1280