git: openjdk/mobile: 8231506: Fix some instabilities in a few networking tests

[duke]

Changeset: 8e98ce54
Author:    Daniel Fuchs <dfuchs at openjdk.org>
Date:      2019-10-01 12:10:33 +0000
URL:       https://github.com/openjdk/mobile/commit/8e98ce54

8231506: Fix some instabilities in a few networking tests

Reviewed-by: alanb, chegar, msheppar

! test/jdk/java/net/MulticastSocket/UnreferencedMulticastSockets.java
! test/jdk/java/net/SocketImpl/SocketImplCombinations.java
! test/jdk/java/net/httpclient/DigestEchoServer.java