Recheck field validation after manually enabling the input field of a ComboGrid
Calling setDisabled(true) on a component makes it valid, but calling setDisabled(false) afterwards did not retrigger a validation check
This fixes a serious bug which was happening in the following
conditions, for instance in the template tab of LXC Wizard:
1) user selects a storage
2) this triggers a reload of a related combogrid
3) this combogrid is marked valid, although its value is empty and it had allowedBlank: false