DO NOT MERGE Updating security string for oc-dev to 2018-05-01

Bug: 74345861
Change-Id: I162bcd6169c91b4f858a05c932d1d58887931945
(cherry picked from commit fa108abad4f1f2a0ecd623c506077869caf053b3)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index ba494ff..ad38a7a 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 := 2018-04-05
+      PLATFORM_SECURITY_PATCH := 2018-05-01
 endif
 
 ifndef PLATFORM_BASE_OS