Fixed possible double deletion of SecurityManager database object

[AGlass0fMilk]

Summary of changes

Fixing possible scenario where dynamically-allocated SecurityManager database object could be deleted multiple times, possibly causing stack corruption and subsequent hard faults.

Related to issue #11768 and MR #11831

Calling SecurityManager::reset now checks to see if the database object has already been deleted before attempting to delete it.

Subsequently, when reinitialized, the call to SecurityManager::init_database also tries to delete the database object without checking if it's NULL.

I'm not sure why deleting the database object in reset and then reinitializing it allows the file to be flushed to non-volatile storage (see #11768 ), while deleting it in the init_database call and then reinitializing it does not appear to flush the database to disk first...

However, this patch fixes both issues for me.

I think we need need to refactor the SecurityManager to address this issue from an architectural standpoint very soon.

Impact of changes

Migration actions required

Documentation

Related to issue #11768 and MR #11831

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Pull request type

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

@paul-szczepanek-arm

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[ciarmcom]

@AGlass0fMilk, thank you for your changes.
@paul-szczepanek-arm @ARMmbed/mbed-os-pan @ARMmbed/mbed-os-maintainers please review.

[paul-szczepanek-arm]

thank you for the fix

[paul-szczepanek-arm]

this is redundant, the fix above is enough

[paul-szczepanek-arm]

Please replace tabs with spaces.
The second change is redundant, the fix in reset is enough to guard against double deletion.

[adbridge]

@AGlass0fMilk could you please address @paul-szczepanek-arm last comments ?

[0xc0170]

@AGlass0fMilk could you please address @paul-szczepanek-arm last comments ?

Once done, let us know to restart tests

[0xc0170]

As requested above by @paul-szczepanek-arm , marking this as request changes.

[AGlass0fMilk]

@paul-szczepanek-arm @0xc0170 Implemented requested changes. Please review.

[0xc0170]

BLE: fix pointer not set to null on delete #12185

Lets continue there. I'll close this one.