Long outage when changing private key

[Derrick Lyndon Pallas]

With two peers, A with persistent keepalive & B without, I am trying to 
change the private key on peer A. First I update the public key for A at 
B, then `wg set wg0 private-key XXXX` on A. It takes roughly the length 
of the persistent keepalive to reestablish pings from B to A.

If instead I update the public key for A at B, remove peer B at A, 
change A's private key, and then re-add peer B at A, I am able to 
reestablish pings almost immediately.

My guess was that there was a timer that needed to be reset when 
wg_set_device processes WGDEVICE_A_PRIVATE_KEY, but an attempt to reset 
timers was unsuccessful. I am new to this code and could use some 
pointers/advice on where to look next.

~Derrick