net: conn: Fix issues with SMP in connection code

When testing on qemu_x86_64 with e1000 Ethernet driver, there are
several crashes due to list management simultaneously executing on
different cores. Add mutexes similar to other parts on networking
stack, for example tcp_lock.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
1 file changed