Remove host_system_image_id column from system_image
This column has been used in the past to represent the relation between an IPMI controller and the main OS on a single piece of hardware, which is better expressed by their both linking to the same hardware; and also to describe which dom0 hosts a domu, which is better expressed by the existing table mm_dom0_domu. We should therefore drop this column. Affects the following:
- view apps.hobbit_config_system_images depends on column host_system_image_id of table system_image
- view apps.hobbit_config_system_images_v2 depends on column host_system_image_id of table system_image
- view hotwire3."10_View/Computers/Autoinstallation_for_COs" depends on column host_system_image_id of table system_image
- view hotwire3."10_View/My_Groups/Computer_Autoinstallation" depends on column host_system_image_id of table system_image
- view hotwire3."10_View/My_Groups/Computers" depends on column host_system_image_id of table system_image
- view _virtualised_hosts_updates depends on column host_system_image_id of table system_image
- rule apps_selfreg_view_upd on view apps.selfreg depends on column host_system_image_id of table system_image