A minor followup change for BPF offload device option stuff

- Correct description and spelling in the code and xml files.
- Add a TODO for refactoring the IpServer constructor.
- Refine the if-statement for starting IP neighbor monitor.

Test: atest IpServerTest
Change-Id: If9c8bc6f785fa80575db56de4e223292e9807ace
diff --git a/Tethering/res/values/config.xml b/Tethering/res/values/config.xml
index 0ea459a..3f5bc90 100644
--- a/Tethering/res/values/config.xml
+++ b/Tethering/res/values/config.xml
@@ -57,7 +57,7 @@
 
     <!-- Use the BPF offload for tethering when the kernel has support. True by default.
          If the device doesn't want to support tether BPF offload, this should be false.
-         Note that this setting could be override by device config.
+         Note that this setting could be overridden by device config.
     -->
     <bool translatable="false" name="config_tether_enable_bpf_offload">true</bool>