In GetCurrentNS, If there is a context-switch between
getCurrentThreadNetNSPath and GetNS, another goroutine may execute in
the original thread and change its network namespace, then the original
goroutine would get the updated network namespace, which could lead to
unexpected behavior, especially when GetCurrentNS is used to get the
host network namespace in netNS.Do.
The added test has a chance to reproduce it with "-count=50".
The patch fixes it by locking the thread in GetCurrentNS.
Signed-off-by: Quan Tian <qtian@vmware.com>
799d3cbf4c