Add necessary sepolicy for update_engine to reserve space on data

Test: serve an OTA, make sure /data/apex/reserved is present
Bug: 172911822

Change-Id: I9f7967c9047ae834eb55a48d56ffc34a7b37f5db
diff --git a/private/file_contexts b/private/file_contexts
index b7c5628..a6b92bc 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -521,6 +521,7 @@
 /data/apex/active/(.*)?		u:object_r:staging_data_file:s0
 /data/apex/backup/(.*)?		u:object_r:staging_data_file:s0
 /data/apex/decompressed/(.*)?    u:object_r:staging_data_file:s0
+/data/apex/ota_reserved(/.*)?       u:object_r:apex_ota_reserved_file:s0
 /data/app(/.*)?                       u:object_r:apk_data_file:s0
 # Traditional /data/app/[packageName]-[randomString]/base.apk location
 /data/app/[^/]+/oat(/.*)?                u:object_r:dalvikcache_data_file:s0