[IT4.6] Unbundle NMS out from ConnectivityManager

ConnectivityService is no longer to update idle timer to NMS but
send to INetd directly after this change. Replace the API
implementation in ConnectivityManager to refer into
ConnectivityService instead of NetworkManagementService to remove
the dependency between CM and NMS for ConnectivityService mainline.

Bug: 170598012
Test: atest FrameworksNetTests
Change-Id: If0ac9a6427dba5a732a15b5d7ca1351b71b07b7b