storaged: allow shell to call dumpsys storaged

Test: adb kill-server && adb shell dumpsys storaged
Bug: 36492915
Change-Id: I3a1a2ad2f016ddd5770d585cae82c8be69001df9
diff --git a/private/storaged.te b/private/storaged.te
index 3dbabf6..698999f 100644
--- a/private/storaged.te
+++ b/private/storaged.te
@@ -21,6 +21,10 @@
   allow storaged debugfs_mmc:file r_file_perms;
 ')
 
+# Needed to provide debug dump output via dumpsys pipes.
+allow storaged shell:fd use;
+allow storaged shell:fifo_file write;
+
 # Binder permissions
 add_service(storaged, storaged_service)