MXCrypto: requestAllPrivateKeys: request cross-signing keys in more cases
MXCrypto: requestAllPrivateKeys: request cross-signing keys in more cases

Request them as long as we cannot cross-sign
matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk