contrail-collector does UVE Updates based on messages from generators.
It also deletes UVE values from redis when generators disconnect.
We saw an instance where updates seems to happen just after a disconnect.
This causes contrail-analytics-api to return stale values for some UVE attributes.

Before the UVEUpdate script writes updates to redis, it should check that the generator
for which the update is being done is still connected (via the NGENERATORS set in redis)

Change-Id: If376bca64f5a8ba5be9eaa72a71d47a275b6eb20
Closes-Bug: #1383896
Merge "contrail-collector does UVE Updates based on messages from generators. It also deletes UVE values from redis when generators disconnect. We saw an instance where updates seems to happen just after a disconnect. This causes contrail-analytics-api to return stale values for some UVE attributes." into R1.10