Allow two cmpctblock requests concurrently.
Allow two cmpctblock requests concurrently.

Sometimes blocks are announced on the network in quick succession. It is
not necessary to request a full-block for the more recent one, but
instead request two cmpctblocks.

Fixes 9318

rebroad/bitcoin,rebroad/bitcoin,rebroad/bitcoin,rebroad/bitcoin,rebroad/bitcoin,rebroad/bitcoin