packaging: suggest path for local storage during AIO setup

When running AIO setup, the installer suggest a default location
(/var/lib/images) for the Local storage domain path the same way
we suggest for the local ISO domain.

Renamed generateIsoDomainName in generateIsoDomainPath in
engine-setup to be more accurate.

Change-Id: Ifb131c3e8d88d6503dc2a03d46fa86590ead52cb
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=896465
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>