Previously, services would obtain the user ID of "service" through
getpwnam(3). While this approach is conceptually better, it also
imposes linking against libc which in turn causes problems with
printf(3), which already led to PFS no longer dropping privileges at
all. For now, we hardcode SERVICE_UID and use that instead.
In the future, two changes should allow removal of SERVICE_UID again:
- "service edit" should cause RS to request that a service (such as
PFS) drop privileges through SEF, using the user ID resolved by
service(8), or something similar;
- a future devfs should make it possible for inet to start without
root privileges altogether.