Remove lock variables from Cover device state attributes

[tetienne]

Some _lock_xxx variables was only used fo within device_state_attributes which is IMO useless. Removing them, we once again ease the code with useless boilerplate.

[iMicknl]

@tetienne I will have a look later today, this is something I will need to test a bit more. I am not 100% sure what the previous code did, since this is coming from the original component.

[tetienne]

@iMicknl Normally the data I removed are not used in the cover behavior. They are here only to be used as HA attributes where you can put what you want.

[vlebourl]

I don't have covers and can't really appreciate those changes, so I put my faith in you :)

[iMicknl]

@tetienne true, but I am not sure if those value are used by automations of people using the current component. I have never used those values, thus I would need to see if this is something where people can depend on.

However, I am up for making the cover platform simpler, since there is still some legacy inside.

[tetienne]

I don't see any reason to use these weird variables. It's not something familiar within HA.

[iMicknl]

Good to have the cover component simplified. If people use the _lock_level or calculated _lock_timer, we will gather their feedback at some point.