Unit tests: fix cellular athandler unit tests and wait() declaration conflict

[lorjala]

Description

Fix failing cellular unit tests on Windows and Mac OS.

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change

[SeppoTakalo]

This needs to be prioritized as it is blocking unittesting in Mac OS X

[0xc0170]

/morph build

[SeppoTakalo]

Btw, unittest building already working:

So why the need of morph build?

[0xc0170]

So why the need of morph build?

Because the rest of the CI is required (the green policy). Now that we have unittests separate CI. We need to find a solution to this and document it. Once all its in place, we can update this.

[mbed-ci]

Build : SUCCESS

Build number : 3122
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8182/

Triggering tests

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

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2731
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8182/

[mbed-ci]

Test : SUCCESS

Build number : 2922
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8182/2922