Support modules to be installed directly to recovery.img

Previously the recovery binary was configured to be installed to the
system.img and then got copied to recovery.img in the recovery.img's
build rule.
With this change, a module, such as the recovery binary, can configure
itself to be installed directly to the recovery.img, just like how other
modules get installed to system.img.

Bug: 19667686
Change-Id: I46b0b4a95cf078a68999db9c0f6635d6a3f5cd86