Avoid segmentation fault when registering a device
Avoid segmentation fault when registering a device

ELL is based on poll_ctl. The same fd can't be tracked twice, this patch
is a temporary solution to avoid crashing the service. Re-design is
required to allow monitor the socket at different modules/layers.

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source