proxy: Fix for real the use of atomic inc for the client ID
proxy: Fix for real the use of atomic inc for the client ID

We still had a race, re-reading the atomic counter after incrementing
it. Another client could have connected and incremented the counter
again.

Use the return value of atomic.Add() to build the client struct.

Signed-off-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>

clearcontainers/proxy,clearcontainers/proxy