Minor inconsistency in incomplete messaging in single Add Non-UM Users workflow

[ssciolla]

I noticed when reviewing #390 that the logic for showing the incomplete message with the name input in the single user workflow for Add Non UM Users is somewhat inconsistent. In handleSubmitClick in UserEnrollmentForm, the check is for (firstName === undefined && lastName === undefined), but in the nameInput block, the incomplete message is shown if either is undefined. This doesn't result in any major bugs, just some inconsistent messaging when you only enter a first name or last name. For instance, if you enter just a first name and hit submit, you only see validation errors, no incomplete message; but then if you leave something else incomplete and hit submit, then you do see the incomplete message.