[2911] replace use_ixfr with request_ixfr

src/bin/xfrin/b10-xfrin.xml

@@ -111,7 +111,7 @@ in separate zonemgr process.
       <varname>class</varname> (defaults to <quote>IN</quote>),
       <varname>master_addr</varname> (the zone master to transfer from),
       <varname>master_port</varname> (defaults to 53),
-      <varname>use_ixfr</varname> (defaults to false), and
+      <varname>request_ixfr</varname> (defaults to yes), and
       <varname>tsig_key</varname> (optional TSIG key name to use).
       The <varname>tsig_key</varname> is specified using a name that
       corresponds to one of the TSIG keys configured in the global