[qa] Fix bug in compactblocks v2 merge

Bug caused the wait_for_block_announcement to be called on the wrong node,
leading to nondeterminism and occasional test failures. Bug was introduced in
merge commit:

d075479 Merge #8882: [qa] Fix race conditions in p2p-compactblocks.py and sendheaders.py

Underlying commits which conflicted were:

27acfc1 [qa] Update p2p-compactblocks.py for compactblocks v2
6976db2 [qa] Another attempt to fix race condition in p2p-compactblocks.py

The first commit changed the test_compactblock_construction function signature
and second commit added code which wasn't updated during the merge to use the
new arguments.

Suhas Daftuar <sdaftuar@chaincode.com> noticed the bug and suggested the fix.