On Linux, mask "/proc/interrupts" and "/sys/devices/system/cpu/cpu<x>/thermal_throttle"
inside containers by default. Privileged containers or containers started
with --security-opt="systempaths=unconfined" are not affected.
Mitigates potential Thermal Side-Channel Vulnerability Exploit
(https://github.com/moby/moby/security/advisories/GHSA-6fw5-f8r9-fgfm).
Also: improve integration test TestCreateWithCustomMaskedPaths() to ensure
default masked paths don't apply to privileged containers.
Refers to https://github.com/moby/moby/pull/49560
Signed-off-by: Sascha Grunert <sgrunert@redhat.com>
