Allow mediaserver to read preloads_data_file

SetupWizard initiates video playback using MediaPlayer API. Media server
should be able to handle preloads file descriptors

Bug: 28855287
Change-Id: I529dd39b25b852787b3d1708a853980cf382f045

mediaserver.te

@@ -132,6 +132,9 @@ allowxperm mediaserver self:{ rawip_socket tcp_socket udp_socket }
 allow mediaserver media_rw_data_file:dir create_dir_perms;
 allow mediaserver media_rw_data_file:file create_file_perms;
 
+# Access to /data/preloads
+allow mediaserver preloads_data_file:file { getattr read ioctl };
+
 ###
 ### neverallow rules
 ###