Convert remaining *_id columns to 64 bit

Note: Performing a change_column on a column with an index is expensive, so
we drop the index if it exists beforehand and add it back unconditionally after.
The latter also fixes the *_id columns missing indexes, such as cloud_volumes.

How to locate 32 bit *_id columns:
  `grep -En "create_table|integer.+_id\b" db/schema.rb | grep -v ":limit => 8"`

Modeled after: db/migrate/20100621174417_convert_ids_to64bit.rb

cc @Fryguy @tenderlove @gmcculloug @bzwei @blomquisg @brandondunne @mkanoor @roliveri @lfu 
New migrations should be created so that your schema.rb shows `:limit => 8` for references (*_id) and `:bigserial` for id columns.

For example:
```
  create_table "vms", id: :bigserial, :force => true do |t|
    ...
    t.integer  "host_id",              :limit => 8
    t.integer  "storage_id",           :limit => 8
    ...
    t.integer  "ems_id",               :limit => 8
```


Yeah, I'll fix that.