ServiceTypeClients will store/access services on MdnsServiceCache in subsequent changes. And MdnsServiceCache can be accessed from looper thread only. So ensure MdnsDiscoveryManager calls to ServiceTypeClients on the looper thread. Bug: 265787401 Test: atest FrameworksNetTests Change-Id: I05e73140da58c029b49057bb0ccfdb8ed7818dfc