Connection closed during bootstrap can cause bootstrap loop

It's possible for the sdk to establish a connection to the server but during bootstrap for the server to terminate the connection. When this happens the SDK can get into a state where the memdclient is already closed and tries to dispatch one of the bootstrap operations.

This leads to the memdclient rejecting the operation with a request cancelled error. If this error is returned for a bootstrap critical operation (e.g. auth) then bootstrap is failed and the error returned to the memdclient dialler.

If bootstrap fails against a node then the dialler will wait a set amount of time before re-attempting bootstrap against that node. This wait does not happen when bootstrap fails with a request cancelled error, like returned in the scenario above. This leads the SDK to immediately retry bootstrap, which can lead to all this retriggering from the top and leading to a loop of bootstrapping.

An effect of this is that we create a large number of buffered readers for connections in rapid succession, each 20MB. This can lead to an explosion in the memory usage of the SDK.