<!-- Describe the issue -->

When our chainstate activation sequence fails and we're running the GUI, we ask the user via a question box whether or not they'd like to re-run the sequence with `fReindex = true`. Fun fact: despite the fact that this sequence is wrapped in a while loop, we only run it twice at most.

https://github.com/bitcoin/bitcoin/blob/7ecb309c4ed1bb9ae6b9a12cbb4f083328edc125/src/init.cpp#L1539-L1556

If they answer yes, the sequence will always fail, because a chainstate will have already been initialized in the original run and `InitializeChainstate` will throw a `std::logic_error`:

https://github.com/bitcoin/bitcoin/blob/7ecb309c4ed1bb9ae6b9a12cbb4f083328edc125/src/validation.cpp#L4573-L4594

This always reproduces. To reproduce:
```
gdb ./src/qt/bitcoin-qt
(gdb) b InitializeChainstate
(gdb) # add breakpoint for the "if (!fLoaded && !ShutdownRequested()) {" line
(gdb) r  # should stop at the breakpoint for InitializeChainstate
(gdb) c  # to advance to the breakpoint for the "if (!fLoaded && !ShutdownRequested()) {" line
(gdb) set fLoaded=false
(gdb) c  # should stop at the breakpoint for InitializeChainstate
(gdb) n  # step through InitializeChainstate to see that it throws
```

We expect the re-run of the chainstate activation sequence to not always fail.

{
    LOCK(cs_main);
     Chec whether we're already initialized by checing for genis in
     m_blocman.m_bloc_iex. Note that we can't use m_chain here, since it is
     set based on the coins db, not the bloc iex db, which is the only
     thing loaded at this point.
    if (m_blocman.m_bloc_iex.count(m_params.GenisBloc().GetHash()))
        retn true;
    try {
        const CBloc& bloc = m_params.GenisBloc();
        FlatFilePos blocPos{m_blocman.SaveBlocToDis(bloc, 0, m_chain, m_params, nullptr)};
        if (blocPos.IsNull()) {
            retn error("%s: writing genis bloc to dis failed", __func__);
        }
        CBlocIex* piex = m_blocman.AddToBlocIex(bloc, m_chainman.m_bt_);
        ReceivedBlocTransactions(bloc, piex, blocPos);
    } catch (const std::runtime_error& e) {
        retn error("%s: failed to write genis bloc: %s", __func__, e.what());
    }
    retn true;
}
void CChainState::LoadExternalBlocFile(FILE* fileIn, FlatFilePos* dbp)