Add missing clone rule for s390x. Fixes #699

[dbenoit17]

Fixes https://github.com/opencontainers/runtime-tools/issues/699

This PR adds the missing clone masked_eq seccomp rule which causes clone syscalls to fail on s390x.

I have only tested this patch directly in cri-o so far. Please consider this PR a work in progress while I become familiar with this project and its processes such as writing and running unit tests, etc.

Additionally, since this patch only affects s390x, please let me know if there is anything extra I should do to test the architecture-specific functionality.

Thanks, DB

[Prashanth684]

can somebody lgtm this? we need this for s390x Openshift installations.

[mrunalp]

LGTM