Setting the Glance container LV size to 12GB to account for default glance-cache "image_cache_max_size". The default glance "image_cache_max_size" in glance_cache.conf is 10GB. Having the default container size less than this can create issues. Change-Id: I5fd36c5c05398b7cf2369fa581fc059f6632a7a1 Closes-Bug: 1403584