MINOR: tools: Impprove hash_ipanon to not hash FD-based addresses

"stdout" and "stderr" are not hashed. In the same spirit, "fd@" and
"sockpair@" prefixes are not hashed too. There is no reason to hash such
address and it may be useful to diagnose bugs.

No backport needed, except if anonymization mechanism is backported.
diff --git a/src/tools.c b/src/tools.c
index 5185204..33bc88e 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -5895,7 +5895,11 @@
 	if (scramble == 0) {
 		return ipstring;
 	}
-	if (strcmp(ipstring, "localhost") == 0) {
+	if (strcmp(ipstring, "localhost") == 0 ||
+	    strcmp(ipstring, "stdout") == 0 ||
+	    strcmp(ipstring, "stderr") == 0 ||
+	    strncmp(ipstring, "fd@", 3) == 0 ||
+	    strncmp(ipstring, "sockpair@", 9) == 0) {
 		return ipstring;
 	}
 	else {