fix wrong parameters passed to EnforceExecExternalProcessPolicy (#1523)

Fixes GCS panic, because OCIProcess for exec external is nil.

For exec external process we don't use OCIProcess field of
ProcessParameters, but instead use the top level CommandArgs,
Environment and WorkingDirectory.

Signed-off-by: Maksim An <maksiman@microsoft.com>

Signed-off-by: Maksim An <maksiman@microsoft.com>

internal/guest/runtime/hcsv2/uvm.go

@@ -492,7 +492,11 @@ func (h *Host) ExecProcess(ctx context.Context, containerID string, params prot.
 	var pid int
 	var c *Container
 	if params.IsExternal || containerID == UVMContainerID {
-		err = h.securityPolicyEnforcer.EnforceExecExternalProcessPolicy(params.OCIProcess.Args, params.OCIProcess.Env, params.OCIProcess.Cwd)
+		err = h.securityPolicyEnforcer.EnforceExecExternalProcessPolicy(
+			params.CommandArgs,
+			processParamEnvToOCIEnv(params.Environment),
+			params.WorkingDirectory,
+		)
 		if err != nil {
 			return pid, errors.Wrapf(err, "exec in container denied due to policy")
 		}