Improve GetOutboundIP to work without internet access

[wolfogre]

If the machine cannot access the internet, it returns a preferred IP address from network interfaces.

[KnisterPeter]

🥳
Thanks

[codecov]

Codecov Report

Merging #1707 (c9e4062) into master (4989f44) will increase coverage by 1.29%.
The diff coverage is 70.32%.

@@            Coverage Diff             @@
##           master    #1707      +/-   ##
==========================================
+ Coverage   61.22%   62.52%   +1.29%     
==========================================
  Files          46       48       +2     
  Lines        7141     7519     +378     
==========================================
+ Hits         4372     4701     +329     
- Misses       2462     2498      +36     
- Partials      307      320      +13     

Impacted Files	Coverage Δ
pkg/common/outbound_ip.go	0.00% <0.00%> (ø)
pkg/container/docker_cli.go	82.23% <ø> (ø)
pkg/container/docker_logger.go	52.08% <ø> (ø)
pkg/container/docker_pull.go	33.33% <ø> (ø)
pkg/container/docker_run.go	14.08% <0.00%> (+0.49%)	⬆️
pkg/container/docker_volume.go	0.00% <ø> (ø)
pkg/container/file_collector.go	37.30% <0.00%> (ø)
pkg/container/host_environment.go	0.00% <0.00%> (ø)
pkg/exprparser/functions.go	66.32% <0.00%> (-1.04%)	⬇️
pkg/model/workflow.go	42.11% <ø> (ø)
... and 21 more

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[ChristopherHX]

I think the caller will still crash the cli prog if you return nil here. The caller does an unconditional .String() in the help text..

The cli could use 127.0.0.1 or [::1] as bind address in this case, but may better fit on the caller side.

[wolfogre]

It's safe to call (net.IP)(nil).String().

And if the caller really don't want a nil, it can check the return.