Connection ID is clobbered in log entries from bucket deletion

In BucketManager::startDestroy() we do

...

std::string connectionId;

connectionId = connection.getId(); // a uint32_t

...BucketDestroyer(..., connectionId, ...)...

The connection ID gets truncated into a char and is then used to initialise the string. As a result, the connection ID in BucketDestroyer is broken.

Master is not affected as this appears to have been resolved during merge.