tools: Warning about last domain deletion should be prior to confirmation

The following patch moves the warning print aobut last domain erasure
prior to the confirmation question.
In case of forceDelete option is used - this warning is not presented.

Bug-Url: https://bugzilla.redhat.com/905370
Change-Id: Id91bd35ad832a4c8b8947c0e86bc0679cef3fa7b
Signed-off-by: Yair Zaslavsky<yzaslavs@redhat.com>