Fix the default interface-interval docs and default value

When the interface-interval parser was changed from uint32 parser to
duration parser, the default value stayed at plain 60 which now means 60
seconds instead of 60 minutes.  Fix the default value and the
documentation to match the reality.

bin/named/config.c

@@ -66,7 +66,7 @@ options {\n\
 	geoip-directory \".\";\n"
 #endif /* if defined(HAVE_GEOIP2) */
 			    "\
-	interface-interval 60;\n\
+	interface-interval 60m;\n\
 	listen-on {any;};\n\
 	listen-on-v6 {any;};\n\
 	match-mapped-addresses no;\n\

doc/arm/reference.rst

@@ -4010,9 +4010,10 @@ Periodic Task Intervals
    :tags: server
    :short: Sets the interval at which the server scans the network interface list.
 
-   The server scans the network interface list every :any:`interface-interval`
-   minutes. The default is 60 minutes; the maximum value is 28 days (40320
-   minutes). If set to 0, interface scanning only occurs when the configuration
+   The server scans the network interface list on every interval as specified by
+   :any:`interface-interval`.
+
+   If set to 0, interface scanning only occurs when the configuration
    file is loaded, or when :any:`automatic-interface-scan` is enabled and supported
    by the operating system. After the scan, the server begins listening for
    queries on any newly discovered interfaces (provided they are allowed by the
@@ -4020,6 +4021,8 @@ Periodic Task Intervals
    gone away. For convenience, TTL-style time-unit suffixes may be used to
    specify the value. It also accepts ISO 8601 duration formats.
 
+   The default is 60 minutes (1 hour); the maximum value is 28 days.
+
 .. _rrset_ordering:
 
 RRset Ordering