1. Fix the gateway_ip form item to prevent wrong verification
2. Fix checkCidr function to make sure correct verification of empty values
3. Fix rule message to match form label with empty value
4. Add `maskClosable = false` to prevent closing the modal by mistake when filling in the form, causing all inputs to be cleared
Change-Id: I55f504b6a457de7ff0dd1017453a1cd800f4610a