Update git submodules

* Update trusty/user/base from branch 'master'
  to 15a3284db5179b585d287039993e09df17be2255
  - Add initial support for gtest
    
    Bug: 138738352
    Change-Id: Ifa8b7eabe3faf5cea2c2bf6bce41fd41075d2be8
    
diff --git a/trusty/user/base b/trusty/user/base
index ddaf728..15a3284 160000
--- a/trusty/user/base
+++ b/trusty/user/base
@@ -1 +1 @@
-Subproject commit ddaf728ffcdc01ac425f869e53deaf6f9b7e5f80
+Subproject commit 15a3284db5179b585d287039993e09df17be2255