Make config profile switches also reflect a different tether setting

[LeonarddeR]

Link to issue number:

None, regression caused by #2385

Summary of the issue:

Since auto tethering is implemented, we are using a _tether property on the braille handler to reflect the internal tethering state, since it can be changed by auto tethering without changing the state in the configuration. However, it seems I/we missed the fact that this internal state should be updated properly as soon as one switches a config profile. If not, which is the current situation, the following will occur.

1. Set NVDA to be manually tethered to focus
2. Create a new config profile that is manually tethered to review
3. Switch profiles
4. When you switch to the review profile, NVDA will still be tethered to focus.

Description of how this pull request fixes the issue:

Sets the internal _tether property according to the configuration on every profile switch.

Testing performed:

@dkager tested the case as described above. I will give auto tethering a test in an hour or two, but expect no issues with that, as the state of tethering is handled by the auto tethering mechanism anyway.

Known issues with pull request:

None

Change log entry:

None

[dkager]

I'm assuming there is no property on the handler to indicate if auto-tethering is enabled or not? I.e. we don't need to get that from config as well?

[LeonarddeR]

There is an auto property that always retrieves the state of auto tethering from the config.