ConnectivityServiceTest: fix flaky tests

This patch adjusts timeouts in ConnectivityServiceTest to fix tests
known to fail spruriously.

Test: ran the following tests 500 times without observing any failure
 - testBackgroundNetworks()
 - testMultipleLingering()
 - testPacketKeepalives()
 - testSatisfiedNetworkRequestDoesNotTriggerOnUnavailable()
 - testSatisfiedThenLostNetworkRequestDoesNotTriggerOnUnavailable()
Bug: 32561414
Change-Id: I184fe7189aac768a65b927cc42eefaf8b1b3f930