Bug 2006637: Problem with populating blocktype_installed_viewtype table

For Blocktype::get_viewtypes() the list it returns is static
so if there are more than one call to it during an upgrade it doesn't
pick up any new viewtypes added after the first call.

In upgrade we need it to not be static

Change-Id: I023b0488929138a597a5a1ad058c2c344e23649f
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
(cherry picked from commit eb7abacb)