Duplicate PUT /account_data/... requests during cross-sign resetting

[bwindels]

Account data keys being set during the reset:

m.secret_storage.key.DsWOEDhEfdmIUuvgGyyc0Qp6g7zFmkoi
m.secret_storage.default_key
m.megolm_backup.v1
m.secret_storage.key.DsWOEDhEfdmIUuvgGyyc0Qp6g7zFmkoi
m.cross_signing.master
m.cross_signing.self_signing
m.cross_signing.user_signing
m.megolm_backup.v1

m.secret_storage.key.<keyId> gets fired twice with an identical request body. m.megolm_backup.v1 also gets sets twice, and bizarrely the body is different between both requests.

I can imagine this also happening during the initial bootstrap of an account after registration, which could be another ~20s delay on an overloaded matrix.org HS.

[jryans]

Agreed this is not ideal, but it could be a bit tricky to untangle safely, so let's look post-release.