As there is no direct setting to change to allow for this, a workaround would be to assign a blank survey to category so the default survey is not received.
First create a blank survey by going to the Administration tab, expand Service Desk, select Survey Templates and click Create New in the top right hand corner.
In the Create New Survey window give the survey a name and fill out the Survey Introduction notifying the end user that they can ignore this survey.
Next assign this survey to a specific area by selecting the Administration tab, Service Desk, Requests/Incidents/Problems, Areas
Then select a Category for which the blank survey should be assigned, select the Edit button in the top right hand corner and select Survey.
Assign the recently created blank survey to this Category and it will override the default survey which is sent out.