Skip links to devices that do not participate in a collective instance.

The set of devices participating in a collective instance can be a subset of
all devices visible to TensorFlow.  During collective param initialization, the
devices in the instance are ordered based on device locality.  However the
DeviceLocality object may have links to devices that are not in that instance.
Subsequent lookup in a map of devices would cause a segfault.

This change skips links to devices in the DeviceLocality object that are not a
part of the collective instance.

PiperOrigin-RevId: 210818621