fix(nextcloud_test): Use host network for docker containers

[provokateurin]

Basically the same as #2601.
Also has the benefit that our testing code gets slightly less complicated.

For some reason the tests were still working just fine in CI, but locally the dashboard and weather_status tests were partially failing because the container couldn't connect to the required external services.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 28.88%. Comparing base (5586e9a) to head (0388713).
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2769   +/-   ##
=======================================
  Coverage   28.88%   28.88%           
=======================================
  Files         373      373           
  Lines      138192   138192           
=======================================
  Hits        39923    39923           
  Misses      98269    98269           

Flag	Coverage Δ		*Carryforward flag
account_repository	98.47% <ø> (ø)
cookie_store	99.48% <ø> (ø)		Carriedforward from 5586e9a
dashboard_app	96.05% <ø> (ø)
dynamite	31.05% <ø> (ø)		Carriedforward from 5586e9a
dynamite_end_to_end_test	61.75% <ø> (ø)		Carriedforward from 5586e9a
dynamite_runtime	85.40% <ø> (ø)		Carriedforward from 5586e9a
interceptor_http_client	97.18% <ø> (ø)		Carriedforward from 5586e9a
neon_dashboard	96.05% <ø> (ø)		Carriedforward from 5586e9a
neon_framework	59.34% <ø> (ø)
neon_http_client	94.32% <ø> (ø)
neon_notifications	100.00% <ø> (ø)		Carriedforward from 5586e9a
neon_rich_text	100.00% <ø> (ø)
neon_storage	94.66% <ø> (ø)
neon_talk	99.45% <ø> (ø)		Carriedforward from 5586e9a
nextcloud	24.36% <ø> (ø)
notifications_app	97.36% <ø> (ø)
notifications_push_repository	98.11% <ø> (ø)
sort_box	90.90% <ø> (ø)		Carriedforward from 5586e9a
talk_app	98.84% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.