Add kernel/tests as net_tests is deprecated in system/extras.

BUG: 27228782
diff --git a/default.xml b/default.xml
index b137fa8..8f7c459 100644
--- a/default.xml
+++ b/default.xml
@@ -382,6 +382,7 @@
   <project path="hardware/ti/omap3" name="platform/hardware/ti/omap3" groups="omap3" />
   <project path="hardware/ti/omap4-aah" name="platform/hardware/ti/omap4-aah" groups="omap4-aah" />
   <project path="hardware/ti/omap4xxx" name="platform/hardware/ti/omap4xxx" groups="omap4" />
+  <project path="kernel/tests" name="kernel/tests" />
   <project path="libcore" name="platform/libcore" groups="pdk" />
   <project path="libnativehelper" name="platform/libnativehelper" groups="pdk" />
   <project path="ndk" name="platform/ndk" groups="generic_fs" />