Rework logging setup for Haskell daemons

This fixes a missing functionality: closing of stdout/stderr when
forking daemons. Without this, starting the daemons from the command
line seems to work, but doing it from utils.RunCmd breaks, since
without closing the standard descriptors, RunCmd never finishes.

The code is not very nice; basically what we need is an actual type
for the LogMode desired (LogConsole, LogStderr, LogFile FilePath), but
the syslog (yes/no and *only*) complicates this even more. I'll think
more on this and probably fix it in master.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>