Make test 1939 not depend on total number of proxies allocated

Test 1939 would previously only pass if no proxies had been allocated
by the time it started. This made it not work for CTS runs.

We changed the test to filter its output to prevent this problem.

Test: ./test/run-test --host 1939
Bug: 73252141
Change-Id: I6643c9ee8e8d57398a2a5baf0871d69941e07dcd