Issue #2088 asked for a wrapper to be created for
`create_stream_if_needed` (called `ensure_stream`) for the 25 times that
`create_stream_if_needed` is called and ignores whether the stream was
created. This commit replaces relevant occurences of
`create_stream_if_needed` with `ensure_stream`, including imports.
The changes weren't significant enough to add any tests or do any
additional manual testing.
The refactoring intended to make the API easier to use in most cases.
The majority of uses of `create_stream_if_needed` ignored the second
parameter.
Fixes: #2088.
