ginstall: do not require loadersig on GFLT platforms

The 42.33 FiberJack image in the field does not have a loadersig. Modern
ginstall assumes that all images contain a loadersig. The 42.33 version
of cwmp invokes ginstall with the "--skiploadersig" flag but later
versions removed this, breaking backward compatibility with older
ginstall images that do not contain a loader.sig.

Change-Id: I12909f54c24b015a4ea2b0d8c147558c377bd6ab
1 file changed