🐛 [RUMF-1021] clear cookie cache before expanding cookie

[bcaudan]

Motivation

Since logs and rum share the same session cookie, we can end up with a cached value with only the first product clearing the value of the second product.

ex:

first product session: logs=1
second product session: logs=1&rum=1
expand first product session: logs=1

Changes

Ensure that we read the up to date cookie value before overwriting it

Testing

unit

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I have gone over the contributing documentation.