Bugfix: Search for explicit ServerArray names before creating them.

Rather than doing a wildcard search for the version, search for the
exact server array names we are trying to create and fail if they exist
already. This allows us to create duplicate farms of servers with the
same version, but uniqe name prefixes.

(Useful mostly in staging...)

Change-Id: I311fc368c21469b8a265e6f1d1a4dc4b1ab17690