Use /proc/thread-self/attr if available
Use /proc/thread-self/attr if available

As suggested by @stephensmalley, Linux >= 3.17 provides /proc/thread-self
symlink so there's no need to use gettid().

Let's use this. If not available, fall back to older method.

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

opencontainers/selinux