logd: start logd service in logd uid

Test: gTest logd-unit-tests, liblog-unit-tests and logcat-unit-tests
      Manual inspect grep '^Cap' /proc/<tid>/status for correct capabilities
Bug: 32450474
Change-Id: Ia6a3872901969a789d4309d410dbfd5f5d17b3ce
diff --git a/logd/logd.rc b/logd/logd.rc
index aecc4be..54349dd 100644
--- a/logd/logd.rc
+++ b/logd/logd.rc
@@ -4,6 +4,7 @@
     socket logdw dgram 0222 logd logd
     file /proc/kmsg r
     file /dev/kmsg w
+    user logd
     group logd system readproc
     writepid /dev/cpuset/system-background/tasks