logd: allow access to system files

- allow access for /data/system/packages.xml.
- deprecate access to /dev/logd_debug (can use /dev/kmsg for debugging)
- allow access to /dev/socket/logd for 'logd --reinit'

Bug: 19681572
Change-Id: Iac57fff1aabc3b061ad2cc27969017797f8bef54