debian: Use DPKG_MAINTSCRIPT_PACKAGE in postinst
debian: Use DPKG_MAINTSCRIPT_PACKAGE in postinst

We were setting the NAME variable to ideascube, but as it turns out dpkg
already sets the DPKG_MAINTSCRIPT_PACKAGE to the name of the package
being handled... which is ideascube.

See the dpkg manual page.

ideascube/ideascube,ideascube/ideascube,ideascube/ideascube,ideascube/ideascube