registry resources should be ensurable

otherwise we can't remove them.

Signed-off-by: Gabriel Filion <gabster@lelutin.ca>
Use of filename in all occurrences is useless

the filename argument is useful for defining a name that is different
from the resource name. This is not what we're doing anywhere so there's
no point in using this argument.

Signed-off-by: Gabriel Filion <gabster@lelutin.ca>