tests: reset fIsBareMultisigStd after bare-multisig tests

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).

The new test was introduced in 1bb5d51.

Author: fanquake

src/test/transaction_tests.cpp

@@ -831,6 +831,7 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
     reason.clear();
     BOOST_CHECK(!IsStandardTx(CTransaction(t), reason));
     BOOST_CHECK_EQUAL(reason, "bare-multisig");
+    fIsBareMultisigStd = DEFAULT_PERMIT_BAREMULTISIG;
 }
 
 BOOST_AUTO_TEST_SUITE_END()