Revert Security String to December

Change-Id: I2ce4534c7c18c375ebec336913062442fc6dfae2
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 550fc70..2c8a21f 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -114,7 +114,7 @@
     #  It must be of the form "YYYY-MM-DD" on production devices.
     #  It must match one of the Android Security Patch Level strings of the Public Security Bulletins.
     #  If there is no $PLATFORM_SECURITY_PATCH set, keep it empty.
-      PLATFORM_SECURITY_PATCH := 2017-01-05
+      PLATFORM_SECURITY_PATCH := 2016-12-05
 endif
 
 ifeq "" "$(PLATFORM_BASE_OS)"