dtrt when only relaybandwidthburst is set

fixes bug 2470

changes/bug2470

+  o Major bugfixes:
+    - If relays set RelayBandwidthBurst but not RelayBandwidthRate,
+      Tor would ignore their RelayBandwidthBurst setting,
+      potentially using more bandwidth than expected. Bugfix on
+      0.2.0.1-alpha. Reported by Paul Wouters. Fixes bug 2470.

src/or/config.c

@@ -3401,6 +3401,8 @@ options_validate(or_options_t *old_options, or_options_t *options,
 
   if (options->RelayBandwidthRate && !options->RelayBandwidthBurst)
     options->RelayBandwidthBurst = options->RelayBandwidthRate;
+  if (options->RelayBandwidthBurst && !options->RelayBandwidthRate)
+    options->RelayBandwidthRate = options->RelayBandwidthBurst;
 
   if (options->RelayBandwidthRate > options->RelayBandwidthBurst)
     REJECT("RelayBandwidthBurst must be at least equal "