healthd: add sepolicy

Change-Id: Ic0351c69d67aa3a6f71f505408c53d642626ebb4

healthd.te

+# healthd seclabel is specified in init.rc since
+# it lives in the rootfs and has no unique file type.
+type healthd, domain;
+permissive healthd;
+type healthd_exec, exec_type, file_type;
+
+init_daemon_domain(healthd)
+unconfined_domain(healthd)
+write_klog(healthd)
+
+