Fix owner restoration and discard across nvstore init

[orenc17]

Description

NVstore didnt discard owner from offsets before usage with flash API

Pull request type

[X] Fix
[ ] Refactor
[ ] Target update
[ ] Feature
[ ] Breaking change

@ARMmbed/mbed-os-storage for your review

[davidsaada]

Thanks for catching this. Looks good.

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2756
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7721/

Triggering tests

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

[mbed-ci]

Test : FAILURE

Build number : 2479
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7721/2479

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2385
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7721/

[0xc0170]

/morph test

[mbed-ci]

Test : FAILURE

Build number : 2480
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7721/2480

[orenc17]

could you please run it again, the failure was not related to the PR

[0xc0170]

/morph test

[mbed-ci]

Test : FAILURE

Build number : 2482
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7721/2482

[0xc0170]

/morph test

[mbed-ci]

Test : SUCCESS

Build number : 2483
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7721/2483