Exclude exe_running_docker_save in the "Set Setuid or Setgid bit" rule

[JPLachance]

What type of PR is this?
/kind bug
/kind rule-update

Any specific area of the project related to this PR?
/area rules

What this PR does / why we need it:
Since the upgrade to Falco 0.18.0, the "Set Setuid or Setgid bit" rule is enabled. That rule reports false positives each time we run a container. For example:

{
    "rule": "Set Setuid or Setgid bit",
    "output": "2019-12-02T21:45:32.802828386+0000: Notice Setuid or setgid bit is set via chmod (fd=<NA> filename=/home/appuser mode=S_IXOTH|S_IROTH|S_IXGRP|S_IRGRP|S_IXUSR|S_IWUSR|S_IRUSR|S_ISGID user=root process=exe command=exe /var/lib/docker/overlay2/d06cc577802ae17ab015005a43d1370a3fdc039af0948cc05d0909e9a4404845/diff container_id=host container_name=host image=<NA>:<NA>) k8s.ns=<NA> k8s.pod=<NA> container=host k8s.ns=<NA> k8s.pod=<NA> container=host",
    "priority": "Notice",
    "output_fields": {
      "user.name": "root",
      "proc.name": "exe",
      "container.id": "host",
      "proc.cmdline": "exe /var/lib/docker/overlay2/d06cc577802ae17ab015005a43d1370a3fdc039af0948cc05d0909e9a4404845/diff",
      "evt.arg.mode": "S_IXOTH|S_IROTH|S_IXGRP|S_IRGRP|S_IXUSR|S_IWUSR|S_IRUSR|S_ISGID",
      "container.name": "host",
      "evt.arg.filename": "/home/appuser",
      "evt.time.iso8601": 1575323132802828300
    }
  }

This event is surrounded by dozens like it every time we start a container.

Adding a simple and not exe_running_docker_save fixes the issue.

Which issue(s) this PR fixes:
I did not file an issue, here is the PR instead!

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

rules(Set Setuid or Setgid bit): fixed a false positive by excluding "exe_running_docker_save"

[Kaizhe]

/lgtm

[poiana]

LGTM label has been added.

Git tree hash: f069d9b9591d8ccb16d626061c2fcc9640a1182b

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fntlnz, Kaizhe

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• rules/OWNERS [Kaizhe,fntlnz]

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[fntlnz]

Thanks @JPLachance !