Revert "On a fatal, abort so we get a core file instead of just exiting."

This reverts commit 428347cf.

Decided we didn't want a core dump on ever fatal, as fatal is used
in other programs instead of just the daemons.

src/common/log.c

@@ -1146,7 +1146,7 @@ void fatal(const char *fmt, ...)
 	log_flush();
 	fatal_cleanup();
 
-	abort();
+	exit(1);
 }
 
 int error(const char *fmt, ...)