Update Security String to 05-05 on release branch
(cherry picked from commit 15d6d5502cb5eb2b2054c8baecadccc4422854c9)

Change-Id: I87774eae158daf803601d42608b81d6803c227bf
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index ad38a7a..a15537e 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -181,7 +181,7 @@
     #  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 := 2018-05-01
+      PLATFORM_SECURITY_PATCH := 2018-05-05
 endif
 
 ifndef PLATFORM_BASE_OS