Better fix for infinite recursion; don't return from exit_cleanup

unless the nesting is already pretty deep, because there are normal
cases where exit_cleanup is nested shallowly.  Patch from Marc Espie,
posted by Brian Poole.

NEWS

@@ -69,7 +69,7 @@ rsync changes since last release
       broken.  (Dave Dykstra)
 
     * Prevent infinite recursion in cleanup code under certain circumstances.
-      (Sviatoslav Sviridov)
+      (Sviatoslav Sviridov and Marc Espie)
 
     * Fixed a bug that prevented rsync from creating intervening directories
       when --relative-paths/-R is set.  (Craig Barratt)

cleanup.c

@@ -63,11 +63,11 @@ void _exit_cleanup(int code, const char *file, int line)
 	extern int log_got_error;
 	static int inside_cleanup = 0;
 
-	if (inside_cleanup != 0) {
+	if (inside_cleanup > 10) {
 		/* prevent the occasional infinite recursion */
 		return;
 	}
-	inside_cleanup = 1;
+	inside_cleanup++;
 
 	signal(SIGUSR1, SIG_IGN);
 	signal(SIGUSR2, SIG_IGN);