Fix missing mmol unit conversion for lastEnacted.bg in openaps.js

[dsnallfot]

Issue:
The OpenAPS pill always shows enacted bg in mg/dl and does not convert units to mmol/l when mmol/l is the chosen user setting.

After some troubleshooting together with @bjornoleh and @JeremyStorring today we found out that there currently is no mmol units conversion in the code for prop.lastEnacted.bg. All other bg conversions in openaps.js works as expected.

Solution:
This PR adds the units conversion for prop.lastEnacted.bg, and resolves the issue.

Testing
The issue was identified while using iAPS as devicestatus uploader, and the code change have been tested to work with iAPS as uploader, but are most likely relevant for openAPS uploads in general (not tested).

Please review when suitable for you, and get back with any questions @sulkaharo @bewest

[bjornoleh]

The fix was confirmed to be working here, also using iAPS. Thanks @dsnallfot!

[bjornoleh]

Before fix:

After fix:

[Der-Schubi]

I can confirm the problem itself using AAPS and NS15

[bjornoleh]

@bewest , this PR solves a problem for mmol users. I have tested it for some time now, and it works as expected here. Perhaps consider merging this? Thanks!