Fix FeatureUser leak in ConnectivityService

In case infinite restoral timer is used for a network feature,
FeatureUser could be keep added but never released if a user
is keep calling "startUsingNetworkFeature".

This patch will add duplication check when adding a FeatureUser
into the list in case infinite restoral timer is used.

Bug: 5043513
Change-Id: I47e7076e217f201454fae33ce596ecdc63cf7908
1 file changed