PullAsync modifies QueryDescription in-place when pulling multiple times on same context

[adrianhall]

Describe the bug

When using PullAsync() on a context twice in a row (even if there are other stuff in the middle), the QueryDescription from
the previous PullAsync is used. This generates a query ID by mistake.

To Reproduce

Integration Unit tests Integration_Push_Tests

[adrianhall]

Fixed as part of #80