Bootstrap handler called twice on bootstrap timeout

If bootstrap times out, the handler is called https://github.com/couchbaselabs/couchbase-cxx-client/blob/7f07e53352d9ec76bb4c8ed612f19f03e2cac784/couchbase/io/mcbp_session.hxx#L699 and https://github.com/couchbaselabs/couchbase-cxx-client/blob/7f07e53352d9ec76bb4c8ed612f19f03e2cac784/couchbase/io/mcbp_session.hxx#L779. I presume this is unexpected, for example a lot of our tests use std::future which leads to an exception.

terminating with uncaught exception of type std::__1::future_error: The state of the promise has already been set.