service: Start services normally when seccomp is disabled

service: Start services normally when seccomp is disabled

When service init file declares seccomp support (procd_set_param seccomp),
but procd is compiled without seccomp support, the service should be
started normally, because seccomp-trace and utrace are not available.

Older procd versions decided about whether to start a service in
seccomp sandbox or not based on existence of seccomp whitelist in the
filesystem. This was recently removed (c8faedc "Do not disable seccomp
when configuration is not found", 2017-09-12) because it could be easy
for attackers to disable seccomp support. This changes is a follow-up
to the mentioned commit. With it, procd decides about whether to use
seccomp sandbox based only on compile-time configuration.

Signed-off-by: Michal Sojka <sojkam1@fel.cvut.cz>
Tested-by: Hans Dedecker <dedeckeh@gmail.com>