Cover: Fix auto-stopping without position state

[farmio]

Description

Fixes auto-stopping covers without position state. Due to processing every (outgoing) telegram in every device we did overwrite the target position with the end position.

Eg. when we want from closed to 50% an UP-Telegram is sent to the bus (because we have no position address) and when reaching 50% a stop() shall be called. When processing this (outgoing) UP-Telegram we were treating it like any UP so target position became 0%.

Now we check if the cover is already moving in the received direction and ignore the telegram if it is.
This implies that also signals from the bus are ignored when the cover is currently travelling in the same direction, to a distinct position from xknx - which is a very rare scenario imho.

Fixes #481

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have performed a self-review of my own code
• The documentation has been adjusted accordingly
• The changes generate no new warnings
• Tests have been added that prove the fix is effective or that the feature works
• The changes are documented in the changelog
• The Homeassistant plugin has been adjusted in case of new config options

[farmio]

Please Squash-merge. I forgot to update changelog.

[coveralls]

Coverage increased (+0.002%) to 93.75% when pulling 272cc21 on farmio:fix-cover-auto-stop into 785d73b on XKNX:master.

[marvin-w]

Looks fine imho. Adding some tests might be useful so that it doesn't break again in the future.