Add tests for incomming syslog messages over TCP.

Rework how fstat and ktrace pattern are specified in the test
arguments. Add tests to check wether syslogd privsep works. This
is done for debug and foreground and daemon mode. Fstat is checked
fo

Rework how fstat and ktrace pattern are specified in the test
arguments. Add tests to check wether syslogd privsep works. This
is done for debug and foreground and daemon mode. Fstat is checked
for chroot and sockets. Ktrace dump is grepped for setting uid and
gid.

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Add regression tests for syslog over TLS.

Test that syslogd sending over TCP does not leak a file descriptor
when it receives a SIGHUP.