Update mbed-coap to version 4.7.1

[anttiylitokola]

Description

Add re-scan routine goto if message is caused user callback
This will fix hard fault when blockwise message sending timeouts. This happens cause same list is manipulated through rx callback.

Pull request type

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

[anttiylitokola]

@yogpan01, please review.

[yogpan01]

Approved. Fixes hardfault on devices which have lossy network like Thread/Mesh.
Please take this in along with #8273 for next Mbed OS patch release.

[teetak01]

@0xc0170 can we get this for next patch release?

[teetak01]

@0xc0170 @adbridge needed for 5.10.2

[adbridge]

@teetak01 Technically this has missed the deadline for 5.10.2 but, I've started the ci for it and if it passes I will try and squeeze it in. If not we will get it in for 5.10.3

[adbridge]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3403
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8404/

Triggering tests

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

[mbed-ci]

Exporter Build : SUCCESS

Build number : 3033
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8404/

[mbed-ci]

Test : SUCCESS

Build number : 3204
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8404/3204