Fix codecov reporting

[bmagyar]

The codecov report have been restored recently but it seems that either uploading doesn't really work or it uploads the wrong thing.

See this chart on how it evolved:
https://app.codecov.io/gh/ros-controls/ros2_control

Or an example from 2 recent PRs:
#771 (comment)

• Coverage 34.61% 32.91% -1.71%

#769 (comment)

• Coverage 34.61% 32.95% -1.67%

Ways to fix this:

• check that the codecov.yaml file is up to date and tests repos we actually have
• ensure that the new test reports are uploaded from the master branch