Fixed lorawan unittests valgrind issues

[AnttiKauppila]

Description

LoRaWAN unit tests are having lots of valgrind issues because of unitialized variables
Those are now fixed

Pull request type

[X] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[AnttiKauppila]

@hasnainvirk please review

[kjbracey]

This is more elegantly and correctly done as lorawan_connect_t conn = { 0 };, although GCC sometimes annoyingly and pointlessly complains about missing braces.

In C++98 you can also do lorawan_connect_t conn = lorawan_connect_t();

C++11 would allow the terser lorawan_connect_t conn{};

[hasnainvirk]

Looks good

[cmonr]

/morph build

[cmonr]

@AnttiKauppila Thanks for the fix!
Puts into the context the quick fix that @hasnainvirk was able to do yesterday.

[hasnainvirk]

@cmonr Yesterday we had 1 hour for the fix. So made sure that valgrind warnings were not fatal. And today Antti completes the task with zero warnings. Thanks for the support.

[mbed-ci]

Build : FAILURE

Build number : 3381
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8453/

[cmonr]

IAR network license issues.
/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3385
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8453/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 3017
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8453/

[mbed-ci]

Test : SUCCESS

Build number : 3187
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8453/3187