Make VDI.open_database reindex the opened database.
Make VDI.open_database reindex the opened database.

Reindexing the database means that is_valid_ref can be used on the
opened database - previously this was returning false even if the given
reference was valid.

Signed-off-by: John Else <37b74501daa612e48fea94f9846ed4ddeb6a8f07@citrix.com>

robhoes/squeezed,koushikcgit/xcp-rrdd,simonjbeaumont/xcp-rrdd,sharady/xcp-networkd,johnelse/xcp-rrdd,djs55/xcp-networkd,koushikcgit/xcp-networkd,djs55/squeezed,djs55/xcp-networkd,koushikcgit/xcp-networkd,johnelse/xcp-rrdd,djs55/xcp-rrdd,koushikcgit/xcp-rrdd,sharady/xcp-networkd,djs55/xcp-rrdd,simonjbeaumont/xcp-rrdd,koushikcgit/xcp-rrdd