Cellular: fixed defect where SIM interface was closed too early

[jarvte]

Description

SIM interface was closed too early in CellularConnectionFSM.cpp causing a crash if APN lookup was enabled and apn configured to '0' in application json.
Crash happened EasyCellularConnection::connect(). Moved SIM interface closing a bit later.

Internal ref to defect: IOTCELL-1122

@AriParkkila please review

Pull request type

[X] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[AriParkkila]

Please push also to mbed-os-5.9

[cmonr]

@jarvte @AriParkkila We're a bit confused. As is, this PR look like it will be going into 5.9.2.
Are y'all saying that this should instead be going to 5.10?

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2422
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7275/

Triggering tests

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

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2052
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7275/

[mbed-ci]

Test : SUCCESS

Build number : 2203
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7275/2203

[AriParkkila]

@cmonr this fix should be good for all 5.9, 5.10 and master.