iproute2: ss - Disable stderr messages by default

Hi,

If use latest ss on older kernel (for example 3.0) there will be
RTNL errors printed and ss will use stats info from /proc because
kernel does not support some diag features. So would not it better
to do not print RTNL errors by default but only when special option was
specified - for example '-E' ?

Or at least add to man page that user can export PROC_ROOT variable to
ss to use /proc by default.

What do you think?

Thanks,