svirt_start_destroy: Add cases for multiple seclabels

Add cases for contain both dac and selinux model seclabels, also
with setting in qemu.conf.

Signed-off-by: Wayne Sun <gsun@redhat.com>
svirt_start_destroy: Add test cases for netfs volume

With virt_use_nfs off when selinux enforcing, domain with image on
nfs will fail to start, domain could start while virt_use_nfs on.

Attach netfs disk to domain and set virt_use_nfs, then testing start
domain.

Signed-off-by: Wayne Sun <gsun@redhat.com>
svirt_start_destroy: Add cases for security_default_confined as 0

Add unconfined cases with security_default_confined as 0 in qemu.conf

Signed-off-by: Wayne Sun <gsun@redhat.com>