Don't rebuild tables after enabling BucketListDB

[SirTyson]

Description

Resolves #4265

After migrating to BucketListDB, TTL and CONTRACT_CODE tables are rebuilt when they should not be. This PR fixes this.

Checklist

• Reviewed the contributing document
• Rebased on top of master (no merge commits)
• Ran clang-format v8.0.0 (via make format or the Visual Studio extension)
• Compiles
• Ran all tests
• If change impacts performance, include supporting evidence per the performance document

[dmkozh]

LGTM, but I think we should wait a bit until 20.4 release lands before merging this.

[marta-lokhova]

LGTM! Will merge as soon as master reopens.

[marta-lokhova]

r+ 575e22d