Only send motor commands if pid is enabled

[garyservin]

🦟 Bug fix

Fixes #184

Summary

Because

1. the code updates the motor speed on every PID cycle here
2. the code sets the speeds to 0 as per this change
3. the code disables the pid when we use the o command as per here,

when we send an o command, the next time the PID loop runs, we set the speed to 0, which doesn't give the motors time to actually spin.

This PR fixes this by actually checking if the PID controllers are enabled before setting the motor speeds. It also changes the PID enable(bool) to enable() and disable() instead.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if it affects the public API)

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[jballoffet]

Thanks @garyservin for contributing to Andino! Changes LGTM.