Integration tests: Use node-0 as DNS server

[Geod24]

Let's see what the CI thinks of this.

[codecov]

Codecov Report

Merging #3096 (ac7e3b1) into v0.x.x (f27135d) will decrease coverage by 8.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           v0.x.x    #3096      +/-   ##
==========================================
- Coverage   87.43%   79.27%   -8.17%     
==========================================
  Files         163      210      +47     
  Lines       16530    18830    +2300     
==========================================
+ Hits        14453    14927     +474     
- Misses       2077     3903    +1826     

Flag	Coverage Δ
integration	26.91% <ø> (?)
unittests	87.31% <ø> (-0.12%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
source/agora/common/Task.d	88.88% <0.00%> (-11.12%)	⬇️
source/agora/test/LocalTransactions.d	86.66% <0.00%> (-4.45%)	⬇️
source/agora/consensus/protocol/Nominator.d	90.87% <0.00%> (-1.70%)	⬇️
source/agora/consensus/state/Ledger.d	90.21% <0.00%> (-0.73%)	⬇️
source/agora/node/Validator.d	93.01% <0.00%> (-0.51%)	⬇️
source/agora/network/Manager.d	82.77% <0.00%> (-0.34%)	⬇️
source/agora/consensus/EnrollmentManager.d	97.35% <0.00%> (-0.30%)	⬇️
source/agora/script/Engine.d	97.59% <0.00%> (-0.16%)	⬇️
source/agora/test/Flash.d	95.12% <0.00%> (-0.11%)	⬇️
agora/submodules/ocean/src/ocean/core/Enforce.d	0.00% <0.00%> (ø)
... and 51 more

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[Geod24]

Well we probably need to cross the Rubicon and parse /etc/resolv.conf for this to work.