Revert "add --selinux-relabel option when creating instack image"

This reverts commit 871a7d869341cc9ad4a757f6e17d638ae1329fe3.

Something about using this option was breaking networking on the vm when it is
started. Specifically, NetworkManager is throwing an AVC:

type=AVC msg=audit(1398442374.613:627): avc:  denied  { unlink } for  pid=1038 comm="NetworkManager" name="resolv.conf" dev="sda3" ino=137360 scontext=system_u:system_r:NetworkManager_t:s0 tcontext=system_u:object_r:etc_t:s0 tclass=file

After logging into the instack vm, you can fix that by running:

restorecon  -v -R /
systemctl restart NetworkManager

Just going to revert this commit for now since we don't need working SELinux to
release.
Automatic commit of package [instack-undercloud] release [0.0.11-1].