[lx-brand] secflags aren't working on processes

[teutat3s]

While debugging a musl libc malloc() segfault with arekinath on matrix we discovered that somehow secflags didn't have any effect on processes in a lx-brand zone on a TritonDataCenter host with PI 20190912T054018Z. The lx-brand zone was a docker zone on triton running alpine:latest (3.10 currently)

This issue is to track this down further and to find out why those secflags worked on his lx-brand zones but not on mine.