bash_completion: Get rid of weird retry logic.

bash_completion: Get rid of weird retry logic.

It's totally unclear what this is supposed to do, as the commit which
introduced it six years ago does not say anything about the space
character being the only "proper" value.

Removing the check fixes an issue that only happens on the first
completion attempt: if a unique completion is possible, the completer
prints this completion as if there were multiple completions possible
instead of completing the command line.