--exclude negates the target path

```shell
# Correct: lints all files in src
ament_cpplint src

# Bug: lints all files in current directory (possibly still excluding some things, I didn't verify that)
ament_cpplint --exclude "some/path.cpp" src

# Correct: workaround that does lint all files in src, excluding the path
ament_cpplint --exclude "some/path.cpp" -- src
```
I assume the way argparse is used to define 'exclude' is defaulting the 'paths' to '.'
I wouldn't be surprised if similar problems exist for other linters.

Only tested this on Iron.