Include "netstat -s" output into cbcollect_info.

It's the same information that's provided in /proc/net/netstat but in
a human-readable form.

Change-Id: I08400afaa11e95b00fa42a6eee1fadef400f9f6e
Reviewed-on: http://review.couchbase.org/32564
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>