Allow adbd to write to /data/adb

adbd writes debugging information to /data/adb
when persist.adb.trace_mask is set. Allow it.

Bug: https://code.google.com/p/android/issues/detail?id=72895

(cherry picked from commit 973877dbc1298ee59dce08397ce8425580cbbbb5)

Change-Id: Ida2e0257c97941ab33ccdab59eb2cde95dca344f
diff --git a/file_contexts b/file_contexts
index ec91425..fce051b 100644
--- a/file_contexts
+++ b/file_contexts
@@ -183,6 +183,7 @@
 /data/resource-cache(/.*)? u:object_r:resourcecache_data_file:s0
 /data/dalvik-cache(/.*)? u:object_r:dalvikcache_data_file:s0
 /data/dalvik-cache/profiles(/.*)? u:object_r:dalvikcache_profiles_data_file:s0
+/data/adb(/.*)?		u:object_r:adb_data_file:s0
 /data/anr(/.*)?		u:object_r:anr_data_file:s0
 /data/app(/.*)?                       u:object_r:apk_data_file:s0
 /data/app/vmdl.*\.tmp(/.*)?           u:object_r:apk_tmp_file:s0