bash-completion: fix local completion (RhBug:1151231)

we will use dnf python api

Reference: https://bugzilla.redhat.com/show_bug.cgi?id=1151231
Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
bash-completion: don't query if we trying to use local file (RhBug:1153543)

Reported-by: Jan Synacek <jsynacek@redhat.com>
Reference: https://bugzilla.redhat.com/show_bug.cgi?id=1153543
Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>