blobstores and solo installations should have a persistent disk.

To not loose the blobstores (and db on solo installations), these
jobs should use a persistent disk.

People will use these examples as a starting point and once they will
update for example a stemcell, they will suddently loose all the blobs
if they haven't configured a persistent disk for these jobs. So we
should provide a sane example.
Merge branch 'persistent_disk_for_blobstore' of https://github.com/duritong/bosh into duritong-persistent_disk_for_blobstore

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>