[ Merge of http://go/wvgerrit/154371 ]
There is a rare race condition experienced by some Android devices
where the a new client property set is being added while another is
being removed. The C++ stl library does not provided thread
protection by default.
This CL adds a new mutex for the client property set map which prevents
multiple threads accessing the property sets concurrently.
Bug: 235238226
Test: GtsMediaTestCases on redfin
Change-Id: I32cf11bfb1332295ba1245071102ff0adc35259d
aaa97a5d60