Fixed Nova changes not triggering a rebuild of libpromises.

"DEPENDENCIES" alone does not generate a real dependency. You need the
name of the target as well. This used to be in the build file before.
Probably just a copy/paste error from 0605ac54a87caea1e116c049c6e.
Merge pull request #494 from kacfengine/nova-build-triggering

Fixed Nova changes not triggering a rebuild of libpromises.