Remove ns_event_loop_thread_start() from NDInterface and ThreadInterface connect()

[yogpan01]

Description

ns_event_loop_thread_start() is incorrectly used at connect() phase, the initial
setup is already done at init() phase and the eventloop thread is correctly initialized.

Also, the usage of ns_event_loop_thread_start() API should be behind MBED_CONF_NANOSTACK_HAL_EVENT_LOOP_DISPATCH_FROM_APPLICATION
flag as application can decide to use main thread for event loop, which will result in linker error for this API call in
case of ARMCC compiler.

Pull request type

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

[yogpan01]

@TeroJaasko @kjbracey-arm @SeppoTakalo Please review.

[kjbracey]

I'd go further and strip it altogether - drop the definition and declaration in the header file.

But this'll do.

[yogpan01]

@0xc0170 @adbridge please take this into MASTER base.

[adbridge]

@yogpan01 please follow the correct instructions in the PR header. i.e. Do not change the structure of this header and please put an x in only one box. On this occasion I will fix it for you.

[TeroJaasko]

Is the CI jammed in "Expected - Waiting for status to be reported" state, or is it really taking 3 days to run them?

[kjbracey]

There's a big CI backlog for 5.9.0rc1 so this fix may have to wait until 5.9.1 or at least a later rc :( We're currently populating the 5.9.1 list.

[TeroJaasko]

@kjbracey-arm: Then we (as in Cloud client Lite) must skip the 5.9.0 release completely, as it does not compile. :-( It is really important for us to get this fixed, even if happened on a later 5.9.0-RC.

[0xc0170]

Thanks @TeroJaasko , we will do our best to get this fix in 5.9.0

[cmonr]

/morph build

[cmonr]

Gonna rerun this due to a status update failure :(

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2156
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/6981/

Triggering tests

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

[mbed-ci]

Test : SUCCESS

Build number : 1946
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/6981/1946

[mbed-ci]

Exporter Build : SUCCESS

Build number : 1783
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/6981/