autotest: test sig is set correctly

Change-Id: Ifceef4aa4b13342788fedc47a275b23379c40f20

BUG=8466
TEST=User/KernelCrash and CrashSender tests

Review URL: http://codereview.chromium.org/4168011
diff --git a/client/bin/site_crash_test.py b/client/bin/site_crash_test.py
index 011c971..8144fe4 100644
--- a/client/bin/site_crash_test.py
+++ b/client/bin/site_crash_test.py
@@ -181,7 +181,7 @@
             exec_name = exec_name_match.group(1)
         else:
             exec_name = None
-        sig_match = re.search('Sig: (\S+)', output)
+        sig_match = re.search('sig: (\S+)', output)
         if sig_match:
             sig = sig_match.group(1)
         else: