run-tests.py must print changed test output no matter what exit code is.

tests/run-tests.py

@@ -176,18 +176,20 b' def run_one(test):'
     ret, out = run(cmd)
     vlog("# Ret was:", ret)
 
-    if ret == 0:
+    diffret = 0
         # If reference output file exists, check test output against it
         if os.path.exists(ref):
             f = open(ref, "r")
             ref_out = f.read().splitlines()
             f.close()
             if out != ref_out:
-                ret = 1
+            diffret = 1
                 print "\nERROR: %s output changed" % (test)
                 show_diff(ref_out, out)
-    else:
+    if ret:
         print "\nERROR: %s failed with error code %d" % (test, ret)
+    elif diffret:
+        ret = diffret
 
     if ret != 0: # Save errors to a file for diagnosis
         f = open(err, "w")