Previously, each NodeConnCB had its own lock to synchronize data structures
used by the testing thread and the networking thread, and NodeConn provided a
separate additional lock for synchronizing access to each send buffer. This
commit replaces those locks with a single global lock (mininode_lock) that we
use to synchronize access to all data structures shared by the two threads.
Updates comptool and maxblocksinflight to use the new synchronization
semantics, eliminating previous race conditions within comptool, and re-enables
invalidblockrequest.py in travis.
mininode.py provides a framework for connecting to a bitcoin node over the p2p
network. NodeConn is the main object that manages connectivity to a node and
provides callbacks; the interface for those callbacks is defined by NodeConnCB.
Defined also are all data structures from bitcoin core that pass on the network
(CBlock, CTransaction, etc), along with de-/serialization functions.
maxblocksinflight.py is an example test using this framework that tests whether
a node is limiting the maximum number of in-flight block requests.
This also adds support to util.py for specifying the binary to use when
starting nodes (for tests that compare the behavior of different bitcoind
versions), and adds maxblocksinflight.py to the pull tester.
