We can call gettxoutproof() with a list of transactions. Currently, if
the first transaction is unspent (and all other transactions are in the
same block), then the call will succeed. If the first transaction has
been spent, then the call will fail. The means that the following two
calls will return different results:
gettxoutproof(unspent_tx1, spent_tx1)
gettxoutproof(spent_tx1, unspent_tx1)
This commit makes behaviour independent of transaction ordering by looping
through all transactions provided and trying to find which block they're in.
This commit also increases the test coverage and tests more failure
cases for gettxoutproof()
This commit fixes the module-level docstrings for the tests and helper
modules in qa. Many of these tests were uncommented previously - this
commit ensures that every test case has at least a minimum level of
commenting.