The link flag was previously not filtered _after_ fetching build args for dockerfile builds, which meant if a plugin exposed that in it's own docker-args-build trigger, it would break deploys.
Additionally, allow for whitespaces between link and volume flags.
While I do not agree with _every_ style change, this will force Dokku to have consistent formatting across all shell scripts, which is arguably a Good Thing™.
The command used to reprocess everything is:
```shell
shfmt -l -bn -ci -i 2 -w .
```
