Fix FD leak in NetworkStack

FD leak happened in IpClientLinkObserver, MyNetlinkMonitor never stop
and socket never been closed. Socket should be close properly when
IpClient shutdown.

Bug: 161330494
CRs-Fixed: 2946756
Change-Id: I398314218a11fea2724cd77a91497440ee309c69
(cherry picked from commit 80b3bc157a45373226ec119494a286f57813475f)
2 files changed