Steps to reproduce:

1. Create Template
2. Attempt to create Discovery Rule

1. 1. Set Update Interval to '0' 
   2. Remove Custom Intervals 
   3. Receive error:
      1. "Item will not be refreshed. Specified update interval requires having at least one either flexible or scheduling interval. [host_discovery.php:587 → CApiWrapper->__call() → CFrontendApiWrapper->callMethod() → CApiWrapper->callMethod() → CFrontendApiWrapper->callClientMethod() → CLocalApiClient->callMethod() → CDiscoveryRule->create() → CDiscoveryRule->checkInput() → CItemGeneral->checkInput() → CApiService::exception() in include/classes/api/services/CItemGeneral.php:360]"
   4. Set Flexible interval to '0' and '1-7;00:00-24:00'
   5. Receive error:
      1. "Item will not be refreshed. Please enter a correct update interval. [host_discovery.php:587 → CApiWrapper->__call() → CFrontendApiWrapper->callMethod() → CApiWrapper->callMethod() → CFrontendApiWrapper->callClientMethod() → CLocalApiClient->callMethod() → CDiscoveryRule->create() → CDiscoveryRule->checkInput() → CItemGeneral->checkInput() → CApiService::exception() in include/classes/api/services/CItemGeneral.php:373]"

Expected:
To have discovery rule not poll, and allow item prototypes to poll only.