LoRaWANTimer UT fixed

[AnttiKauppila]

Description

LoRaWAN_Timer unittest was segfaulting, this is fixed now

Pull request type

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

[AnttiKauppila]

@TeemuKultala please review

[cmonr]

Will LoRaWAN unit tess no longer have debug statements? Or did it never have them to begin with?

[AnttiKauppila]

The change is only for LoRaWANTimer class, not the whole LoRaWAN test set

[adbridge]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3627
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8727/

Triggering tests

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

[mbed-ci]

Exporter Build : FAILURE

Build number : 3234
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8727/

[cmonr]

Export nodes got stuck.

Will relaunch when able.

[mbed-ci]

Test : FAILURE

Build number : 3410
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8727/3410

[0xc0170]

Note: This PR is now a part of a rollup PR (#8753).

In order to expedite remaining CI testing, this PR has been bundled into the above rollup PR.

No further work is needed here, as once that PR is merged, this PR will also be closed and marked as merged.

If any more commits are made in this PR, this PR will remain open and have to go through CI on its own.

[cmonr]

Please ignore. I derped.