Now that avalanche is enabled by default, the node might park blocks pending
for polling after an upgrade. We can just unpark the checkpointed blocks upon
startup instead.

Start bitcoind on mainnet, let it run out of IBD. Park a block shortly before the most recent checkpoint:

src/bitcoin-cli parkblock 00000000000000000036e1c7ca4d2c0d3de84fc5ba2a720a226eb14ab612ec0f

Check the result with the getchaintips RPC.

Stop and restart bitcoind, verify that the entire chain is unparked with getchaintips.
Look for the log message Unparking checkpointed block 00000000000000000b360176b8456de45b662fce6d557c6238dec17362d197f3 ... (this is the hash of the most recent checkpoint).