Relax permissions on /data/misc/logd

Incidentd needs to access /data/misc/logd to get persisted logs for
debugging purposes. Relax permissions on /data/misc/logd to allow
group (log) to access the dir and read its files. Effectively change
to:
drwxr-x--- logd log /data/misc/logd
-rw-r----- logd log /data/misc/logd/logcat*

Since this dir stores the past output of logcat, anyone that can run
logcat can be granted access to this dir. Access to this dir is further
guarded by SELinux. So it is safe.

Bug: 147924172
Test: Build, flash, reboot. Verify that the files have the right
      permissions.

Change-Id: I4d2aa9d5883d1ef14411b2b3902f0ca7c641dd7e