fix: fix xline_update_node test and update comments

[themanforfree]

Please briefly answer these questions:
#531

• what problem are you trying to solve? (or if there's no problem, what's the motivation for this change?)
  fix xline_update_node test
• what changes does this pull request make?
  update node to an available address.
• are there any non-obvious implications of these changes? (does it break compatibility with previous versions, etc)
  no

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (8fb8a49) 63.42% compared to head (917f173) 63.41%.

Files	Patch %	Lines
curp/src/client.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #540      +/-   ##
==========================================
- Coverage   63.42%   63.41%   -0.01%     
==========================================
  Files         101      101              
  Lines       18541    18542       +1     
  Branches    18541    18542       +1     
==========================================
- Hits        11760    11759       -1     
- Misses       6048     6051       +3     
+ Partials      733      732       -1     

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[iGxnon]

LGTM