cdrom: fix cdrom change media

Change media operation should not remove device and just change
the source, so fix the implementation from detach then attach
to updateDeviceFlags.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
cdrom: update model test for media update

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Fix typo on API.json and add missing error messages

Instead of storages_create and storages_update they should be
vmstorages_create and vmstorages_update.
Fix it in order to use jsonschema to validate data while adding/updating
vm cdrom.

Signed-off-by: Aline Manera <alinefm@br.ibm.com>