Revert "Revert "Switch "system/core/base" ref to "system/libbase"""

This reverts commit 2f77d1adc806f0d2332dca1dce554a341220849e.

Reason for revert: Applying a Fix to DS directly.  No need for merged-In, since the topic is already landed in DS branch

Change-Id: I86cba9b20efebc9e700522e1697bc8f893c43089
diff --git a/base b/base
deleted file mode 120000
index 622c552..0000000
--- a/base
+++ /dev/null
@@ -1 +0,0 @@
-../libbase
\ No newline at end of file