If gossip_store is an incorrect version, we will recreate it: with an incorrect
version! This means we never get persistent gossip, *and* the pay plugin will
fail to map the gossip_store. Everyone will be sad.
Debugged-by: Matt Whitlock
Fixes: #4376Fixes: #4288
Typing-by: Rusty Russell <rusty@rustcorp.com.au>