Run the tests in a fixed order.

These changes will be passed upstream.

--- serf-1.3.9/build/check.py.orig	2017-03-07 06:59:14.158690090 +0000
+++ serf-1.3.9/build/check.py	2017-03-07 06:59:39.506830744 +0000
@@ -51,7 +51,7 @@
   TEST_ALL_EXE = os.path.join(test_builddir, TEST_ALL_EXE)
 
   # Find test responses and run them one by one
-  for case in glob.glob(testdir + "/testcases/*.response"):
+  for case in sorted(glob.glob(testdir + "/testcases/*.response")):
     print "== Testing %s ==" % (case)
     try:
       subprocess.check_call([SERF_RESPONSE_EXE, case])