Bug 4393: Scan Indexes results cannot be sorted

Bug 4393: Scan Indexes results cannot be sorted

Because of the way Scan Indexes works, the results cannot be sorted. Previously
when any sort other than relevance (or in some cases popularity) was used, the
search failed. This patch disables sorting on Scan results. This patch also
fixes the index selection dropdown on the results page, which was not being
populated correctly from the Advanced Search screen.

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>