Change default max-recursion-queries to 50

Changing the default for max-recursion-queries from 100 to 32 was too
strict in some cases, especially lookups in reverse IPv6 trees started
to fail more frequently. From issue #4921 it looks like 50 is a better
default.

Now that we have 'max-query-count' as a global limit of outgoing queries
per client request, we can increase the default for
'max-recursion-queries' again, as the number of recursive queries is
no longer bound by the multiple of 'max-recursion-queries' and
'max-query-restarts'.

(cherry picked from commit 84df920d9e)

bin/named/config.c

@@ -174,7 +174,7 @@ options {\n\
 	max-clients-per-query 100;\n\
 	max-ncache-ttl 10800; /* 3 hours */\n\
 	max-recursion-depth 7;\n\
-	max-recursion-queries 32;\n\
+	max-recursion-queries 50;\n\
 	max-query-count 200;\n\
 	max-query-restarts 11;\n\
 	max-stale-ttl 86400; /* 1 day */\n\

doc/arm/reference.rst

@@ -4704,7 +4704,7 @@ Tuning
    need to be sent before an answer is reached, then recursion is terminated
    and a SERVFAIL response is returned to the client. (Note: if the answer
    is a CNAME, then the subsequent lookup for the target of the CNAME is
-   counted separately.) The default is 32.
+   counted separately.) The default is 50.
 
 .. namedconf:statement:: max-query-restarts
    :tags: server, query