Remove destruction of WiFi interface in test runs

[SeppoTakalo]

Description

Most of our IP stacks don't allow removal of interfaces so
interface destructor can not reliably clean up. Therefore we
cannot rely its behaviours in test case.

Instead run interface->disconnect() in case interface was already
created.

Status

READY

Migrations

NO

[0xc0170]

@SeppoTakalo Can you please rebase from latest master please, will fix travis timeout.

[betzw]

Isn't this somehow changing the behavior of the tests in the sense that disconnecting - as far as I understand - should/would maintain previously set credentials?!?

[SeppoTakalo]

Rebased.

@betzw Very valid point.
The testcase WIFI-CONNECT-NOCREDENTIALS actually depends on the fact that no credentials have been fed to the driver. Therefore I now moved it to be very first test case after a constructor.

[0xc0170]

/morph build

[mbed-ci]

Build : FAILURE

Build number : 740
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/5723/

[0xc0170]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 755
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/5723/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 406
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/5723/

[mbed-ci]

Test : FAILURE

Build number : 579
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/5723/579

[cmonr]

/morph test

[mbed-ci]

Test : SUCCESS

Build number : 600
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/5723/600