Force writing the timezone

[imobachgs]

Problem

YaST is rewriting the timezone settings. See #903.

Solution

• Write the locale settings on a single call.
• Mock the InstFunctions module to avoid loading some code when asking whether the second stage will be executed (no second stage in Agama). This code ended up writing the timezone with the wrong value.

Testing

• Tested manually

[coveralls]

coverage: 75.35% (+0.006%) from 75.344%
when pulling 6ebe3ba on force-timezone
into c34f5c7 on master.

[imobachgs]

After some tests, the real problem seems to be that YaST is overwriting the localtime. I need to rethink the solution.

[dgdavid]

Reading the code looks good. So, if you've tested that it works... Just go ahead!