Fix runc exec on big-endian, causing:
container_linux.go:265: starting container process caused "open /dev/pts/4294967296: no such file or directory"
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit aab5eaddccb8cb196fdb1e285890dfa94a071b14)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>