Fixed a bug in the logic for finding available sockets for testing.

Maybe this will reduce the chance if spurious test failures due to
addresses already in use.  Unfortunately, there's still a race that
may make running tests in parallel impractical until it's addressed.

src/ZEO/tests/forker.py

@@ -220,10 +220,20 @@ def get_port():
         try:
             try:
                 s.connect(('localhost', port))
+            except socket.error:
+                pass  # Perhaps we should check value of error too.
+            else:
+                continue
+
+            try:
                 s1.connect(('localhost', port+1))
             except socket.error:
-                # Perhaps we should check value of error too.
+                pass  # Perhaps we should check value of error too.
+            else:
+                continue
+
             return port
+
         finally:
             s.close()
             s1.close()