Use a delayed message to schedule the query task

To reduce the multi-thread access to MdnsServiceTypeClient, the
query task scheduling should be replaced with a delayed message.
This will allow the synchronized lock to be removed in future
changes.

Bug: 265787401
Test: atest FrameworksNetTests
Change-Id: I340fe1a407947be860cdcd9c7c76829417a32e4c
3 files changed