Logsys: Ensure logging PID is really corosync

When serivce plugin calls fork and child uses logsys, it may lead to
corrupted fdata (idx is updated but it's not shared between child and
parent, but fdata is mmaped file and this is shared).

Solutions is to:
- Store corosync pid
- On log, check if current pid == corosync pid
- If so -> store in fdata, if not -> don't store

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>
fplay: Check minimum record size

For records in fdata smaller then 4 display error, because such record
is invalid.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>
corosync-fplay: Check incorrect idx and cycle

If idx is too large, segfault can happen. Also cycle is now detected
properly.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>