Use crossystem rather than cros_boot_mode.

Also, make the check for normal mode a bit more restrictive.

BUG=chromium-os:13283
TEST=unit tests, tested on device

Change-Id: I3ec8a4c5526208d6f050ec2e152604b2ead76f27

Review URL: http://codereview.chromium.org/6719012
diff --git a/omaha_request_action_unittest.cc b/omaha_request_action_unittest.cc
index 7e67555..ece5a7d 100755
--- a/omaha_request_action_unittest.cc
+++ b/omaha_request_action_unittest.cc
@@ -603,7 +603,7 @@
       "errorcode=\"%d\"></o:event>\n",
       OmahaEvent::kTypeDownloadComplete,
       OmahaEvent::kResultError,
-      kActionCodeError | kActionCodeBootModeFlag);
+      kActionCodeError);
   EXPECT_NE(post_str.find(expected_event), string::npos);
   EXPECT_EQ(post_str.find("o:updatecheck"), string::npos);
 }