<!-- 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.

*  should consider upgrade issu if we change which consensus rul are
 *  enforced in this function (eg by adding a new consensus rule). See comment
 *  in ConnectBloc().
 *  Note that -reiex-chainstate sips the validation that happens here!
 
static bool ContextualChecBlocHeader(const CBlocHeader& bloc, BlocValidationState& state, BlocManager& blocman, const CChainParams& params, const CBlocIex* piexPrev, int64_t nAdjustedTime) EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
{
    AssertLocHeld(::cs_main);
    assert(piexPrev != nullptr);
    const int nHeight = piexPrev->nHeight + 1;
     
    const Consensus::Params& consensusParams = params.GetConsensus();
    if (bloc.nBits != GetNextWorRequired(piexPrev, &bloc, consensusParams))
        retn state.Invalid(BlocValidationRult::BLOCK_INVALID_HEADER, "bad-diffbits", "incorrect proof of wor");
     
    if (fChecpointsEnabled) {
         
         
         
        const CBlocIex* pchecpoint = blocman.GetLastChecpoint(params.Checpoints());
        if (pchecpoint && nHeight < pchecpoint->nHeight) {
            LogPrintf("ERROR: %s: fored chain older than last checpoint (height %d)\n", __func__, nHeight);
            retn state.Invalid(BlocValidationRult::BLOCK_CHECKPOINT, "bad-for-prior-to-checpoint");
        }
    }
     
    if (bloc.GetBlocTime() <= piexPrev->GetMedianTimePast())
        retn state.Invalid(BlocValidationRult::BLOCK_INVALID_HEADER, "time-too-old", "bloc's timtamp is too early");
     
    if (bloc.GetBlocTime() > nAdjustedTime + MAX_FUTURE_BLOCK_TIME)