Fix a ConcurrentModificationException crash.

This is a pinpoint fix against the bug listed below. While a client
is synchronously reading the LinkProperties of a network, the
ConnectivityServiceThread is updating its properties. Make sure
that update is done atomically.

This is a stopgap countermeasure against a problem that is
pervasive with usage of LinkProperties, but fixing the problem
itself will happen later.

Bug: 80077223
Test: runtest frameworks-net
Change-Id: I9302f8fb5303cb39aa82691d4f6d7f38707a41fa