Improve robustness of stream socket tests

Make the test more robust by waiting for the expected error state to
be reached. "broken pipe" is the initial error sender gets when trying
to write to the disconnected socket, but it can not be reliably
observed due to lack of synchronization between the sender thread and
the test body.

src/test/java/com/timgroup/statsd/UnixStreamSocketTest.java

@@ -34,6 +34,11 @@ public synchronized void handle(Exception exception) {
         lastException = exception;
     }
 
+    synchronized boolean lastExceptionMessageContains(String s) {
+        String msg = lastException.getMessage();
+        return msg != null && msg.contains(s);
+    }
+
     @BeforeClass
     public static void supportedOnly() throws IOException {
         Assume.assumeTrue(TestHelpers.isUdsAvailable());
@@ -108,22 +113,19 @@ public void resist_dsd_restart() throws Exception {
 
         // Close the server, client should throw an IOException
         server.close();
-        while(lastException.getMessage() == null) {
+        while(!lastExceptionMessageContains("Connection refused")) {
             client.gauge("mycount", 20);
             Thread.sleep(10);
         }
-        // Depending on the state of the client at that point we might get different messages.
-        assertThat(lastException.getMessage(), anyOf(containsString("Connection refused"), containsString("Broken pipe")));
 
         // Delete the socket file, client should throw an IOException
         lastException = new Exception();
         socketFile.delete();
 
         client.gauge("mycount", 21);
-        while(lastException.getMessage() == null) {
+        while(lastExceptionMessageContains("No such file or directory")) {
             Thread.sleep(10);
         }
-        assertThat(lastException.getMessage(), containsString("No such file or directory"));
 
         // Re-open the server, next send should work OK
         DummyStatsDServer server2;