Cortex polling settings break startup

### Request Type
Bug

### Work Environment
TheHive 3.1.1

### Problem Description
From version 3.0.1, the Cortex job polling is configurable by defining the time between two polls (`cortex.refreshDelay`) and the number of consecutive failures before giving up (`cortex.maxRetryOnError`). These settings prevent TheHive to start because it tries to interpret them as Cortex server section.