Fix service start

[tadaskay]

#3379 added required Price for service start request in tequila. This removes the requirement and also allows using pre-saved config values for service pricing (previous web UI behavior) to make it easier to consume.

[tomasmik]

I think CI will mention this, but if it doesn't I think swagger also needs an update now.

[codecov-commenter]

Codecov Report

Merging #3404 (4ee28c1) into master (4f9b967) will increase coverage by 0.04%.
The diff coverage is 43.04%.

@@            Coverage Diff             @@
##           master    #3404      +/-   ##
==========================================
+ Coverage   43.62%   43.66%   +0.04%     
==========================================
  Files         320      311       -9     
  Lines       14045    13667     -378     
==========================================
- Hits         6127     5968     -159     
+ Misses       7199     6979     -220     
- Partials      719      720       +1     

Impacted Files	Coverage Δ
ci/release/debian.go	0.00% <ø> (ø)
communication/nats/connection_wrap.go	69.23% <0.00%> (-10.19%)	⬇️
communication/nats/logger.go	33.33% <ø> (ø)
config/flags_chains.go	61.40% <0.00%> (ø)
config/flags_location.go	0.00% <0.00%> (ø)
config/flags_network.go	0.00% <0.00%> (ø)
config/flags_payments.go	0.00% <0.00%> (ø)
config/flags_service_noop.go	0.00% <0.00%> (ø)
config/flags_service_openvpn.go	0.00% <0.00%> (ø)
config/flags_service_start.go	0.00% <0.00%> (ø)
... and 83 more

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