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.
If node 0 is sufficiently fast to announce its block to node 1,
node 1 might already have the block by the time the
node_sync_via_rpc loop gets around to node 1, resulting in the
submitblock result "duplicate-inconclusive" as node 1 has the block,
but prefers an alternate chain.
