Rename nodepool exta-data.d to extra-data.d

The exta-data.d name was a typo and prevented us from installing the
nodepool scripts on our dib built images. Move this dir to the correct
name, extra-data.d, so that nodepool scripts are properly installed.

Change-Id: I0b7c926caf55b89687075800bff59428069f4889
Merge "Rename nodepool exta-data.d to extra-data.d"