Add code to verify if external Wifi module is still responsible

[tymoteuszblochmobica]

DNS timeout test fixed to mitigate ESP8266 Wifi module low performance.

Description (required)

DNS timeout test requires flooding device with DNS queries.
After this test finishes gethostbyname check is performed to ensure the device is still alive.

Summary of change (What the change is for and why)

DNS timeout test requires flooding device with DNS queries.
This causes problem to ESP8266 module causing it to stuck for 11 sec.
In result all following tests fails. To avoid this "smart delay" is added.
If device preforms gethostbyname correctly then tests can proceed, otherwise after 1 sec sleep gethostbyname is repeated until success or re-check limit (set to 15).
Thanks to this all ethernet and non ESP8266 wireless devices don't need to wait but ESP must wait.

Documentation (Details of any document updates required)

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Pull request type (required)

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results (required)

[] No Tests required for this change (E.g docs only update)
[x] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers (optional)

@SeppoTakalo
@AnttiKauppila

Release Notes (required for feature/major PRs)

Summary of changes

DNS timeout test module fix

Impact of changes

Migration actions required

[michalpasztamobica]

I generally like this solution more than the blind sleep.
But let's not merge this before this fix gets verified: #11817

[ciarmcom]

@tymoteuszblochmobica, thank you for your changes.
@AnttiKauppila @SeppoTakalo @ARMmbed/mbed-os-test @ARMmbed/mbed-os-ipcore @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

DNS timeout test requires flooding device with DNS queries.
This causes problem to ESP8266 module causing it to stuck for 11 sec.
In result all following tests fails. To avoid this "smart delay" is added.
If device preforms gethostbyname correctly then tests can proceed, otherwise after 1 sec sleep gethostbyname is repeated until success or re-check limit (set to 15).
Thanks to this all ethernet and non ESP8266 wireless devices don't need to wait but ESP must wait.

@tymoteuszblochmobica Please provide these details in the commit msg. I've noticed in another PR, similar thin: very brief commit messages. It only helps if you can add these there.

Once updated, we will start CI

[tymoteuszblochmobica]

Updated commit msg.

[0xc0170]

But let's not merge this before this fix gets verified: #11817

Set to preceding PR, will wait

[michalpasztamobica]

@0xc0170 , can you help us figure out what the problem is? When we click "Details" we get 404 error.

[0xc0170]

pr-merge fixed (was internal error).

@michalpasztamobica As this still waits for another PR , is there anything we can do here?

[michalpasztamobica]

@0xc0170 , I thought the other PR would come in faster, so perhaps I take back my original idea to wait... This PR is approved by Antti, lets merge it in.
It is an improvement over a fixed 12s delay, which we have right now. In case Antti's solution proves right, then we can remove it (instead of removing the fixed 12s delay). No point to keep it open, as it still is an improvement over the current situation.

[0xc0170]

@AnttiKauppila Please review the suggestion above and let us know if we proceed with this one for 5.15 ?

[michalpasztamobica]

@AnttiKauppila , would you please, review again, this time - just to approve that this can go in now, without waiting for the ESP8266 fix being validated (that might take a while)?

[michalpasztamobica]

@0xc0170 this seems ready for CI 🚀

[0xc0170]

CI restarted

[mbed-ci]

Test run: SUCCESS

Summary: 5 of 5 test jobs passed
Build number : 1
Build artifacts