create-image.sh: fix sed expression that was duplicating entries in grub.cfg.
create-image.sh: fix sed expression that was duplicating entries in grub.cfg.

Fixes #128

lebauce/edeploy,lebauce/edeploy,lebauce/edeploy,redhat-cip/edeploy,enovance/edeploy,enovance/edeploy,redhat-cip/edeploy,enovance/edeploy,enovance/edeploy,redhat-cip/edeploy,lebauce/edeploy,redhat-cip/edeploy