Bug 1163036 - <oo-install> fix crash when moving districts

https://bugzilla.redhat.com/show_bug.cgi?id=1163036

- previously if only one district was defined and you tried to move
  the host district, the installer would crash.
Merge pull request #496 from detiber/bz1163036

Bug 1163036 - <oo-install> fix crash when moving districts