Log: attrd,pacemakerd,libcrmcommon: make "Exiting" last message

Previously, pacemakerd would log an "Exiting" message, then call crm_exit(),
which could log more messages. Now, crm_exit() logs the "Exiting" message,
after doing everything else.

This will result in more logs (i.e. every call of crm_exit()), but they will be
at info level, and potentially useful.