Use common data dir

Paths get stuffed in the database so rather than rewrite them
just leave the data in-place for both versions.  This is how
real upgrades are likely to be done anyway...

Change-Id: I3610d93227b54d4c2f5c832478e7d23afe1bd173
Re-force the Folsom-era Cirros image

Change-Id: I7bb90bc029cff536054f0b24bbf25f53f6c2cfc9
Merge branch 'common-data' into dt-test
Merge branch 'cirros-image' into dt-test