Docs: Add "admin" to samples categories

Contains samples for device administration APIs.

Issue: 18544051
Change-Id: I8e157ba163848ac0356f2669a9cadd0f76b4ae9a
diff --git a/Android.mk b/Android.mk
index 75e32c1..da98b19 100644
--- a/Android.mk
+++ b/Android.mk
@@ -727,7 +727,8 @@
 # Whitelist of valid groups, used for default TOC grouping. Each sample must
 # belong to one (and only one) group. Assign samples to groups by setting
 # a sample.group var to one of these groups in the sample's _index.jd.
-sample_groups := -samplegroup Background \
+sample_groups := -samplegroup Admin \
+                 -samplegroup Background \
                  -samplegroup Connectivity \
                  -samplegroup Content \
                  -samplegroup Input \