Description of problem:
The behaviour is different if don't specify security label for static type between rhel6 and rhel7 

Version-Release number of selected component (if applicable):
virt-install-1.2.1-8.el7.noarch

How reproducible:
100%

Steps to Reproduce:
RHEL7:
# virt-install -n demo -r 1024 -f /var/lib/libvirt/images/demo.img -s 5 -l http://download.englab.nay.redhat.com/pub/rhel/rel-eng/RHEL-7.2-20151030.0/compose/Server/x86_64/os/ --security type='static'

Starting install...
Retrieving file vmlinuz...                                                                                                                                                                  9.8 MB  00:00:00 !!!
Retrieving file initrd.img...                                                                                                                                                                76 MB  00:00:03 !!!
ERROR    XML error: security label is missing
Domain installation does not appear to have been successful.
If it was, you can restart your domain by running:
  virsh --connect qemu:///system start demo
 otherwise, please restart your installation.

 RHEL6:
 #  virt-install -n demo -r 1024 -f /var/lib/libvirt/images/demo.img -s 5 -c /tmp/RHEL5.5-Server-20100322.0-x86_64-DVD.iso --security type='static'
 ERROR    A label must be specified for static security type.

Actual results:
The error is returned after installation begins and the image file is created for rhel7.
The error is returned before installation begins for rhel6.

Expected results:
I think the behavior for rhel6 is better because it will not create any files when error occurs and keep the env more cleaner.

Additional info: