This fixes a bug in the unit tests that was introduced in D8308
> The bug this fixes is two-part.
>
> 1.The fIsBareMultisigStd global is being reused by other tests,
> i.e script_p2sh_tests(set), after being set to false.
>
> 2. The order our tests run in doesn't always? seem to be random,
> which meant that the script_p2sh tests would only fail if they
> were run in an order where transaction_tests ran first, mutating
> the fIsBareMultisigStd global.
>
> This doesn't seem to happen when running make check, but if you
> run src/test/test_bitcoin and pass --random=99999, the failure
> in script_p2sh:
>
> test/script_p2sh_tests.cpp:200: error: in "script_p2sh_tests/set": txTo[1].IsStandard
>
> will occur (on most systems).
This is a backport of Core PR18018