DO NOT MERGE: remove system_server sdcard_type

klp-modular-dev-plus-aosp has a rule allowing system_server
access to sdcard file descriptors, but this change isn't
in AOSP nor internal master.

This line was removed in https://android-review.googlesource.com/84081 .
Pull the line out from the -plus-aosp tree. DO NOT MERGE because
this change is already in internal master.

Change-Id: I0a1b08f75d309a5a1acb5dc1a44212f9d35eaf3e