bugfix: potential abort during HUP

This could happen when one of imklog, imzmq3, imkmsg, impstats,
imjournal, or imuxsock were under heavy load during a HUP.
closes: http://bugzilla.adiscon.com/show_bug.cgi?id=489
Thanks to Guy Rozendorn for reporting the problem and Peval Levhshin for
his analysis.