`set_current_mode` bypasses `pysmurf` interface

[tristpinsm]

There is code in util.py:set_current_mode that bypasses the pysmurf interface and accesses hardware registers directly. This is not supported and could easily break in the future.

Should figure out why this was deemed necessary and implement sufficient functionality in pysmurf for this operation.

[tristpinsm]

tagging @msilvafe in case you have some insight -- not an urgent thing

[msilvafe]

It's alluded to in the docstring but I think the full discussion of heating and how this function improved things is discussed in this PR where this function was added: #171 (comment)