logging: add interface to start/stop syslog units

Required for example to start/stop systemd-journal-flush.service
which moves the journal storage back and forth between tmpfs and
permanent storage.

Signed-off-by: Luca Boccassi <luca.boccassi@microsoft.com>

policy/modules/system/logging.if

@@ -427,6 +427,24 @@ interface(`logging_domtrans_syslog',`
 	')
 ')
 
+########################################
+## <summary>
+##	Allow specified domain to start/stop syslog units
+## </summary>
+## <param name="domain">
+##	<summary>
+##	Domain allowed access.
+##	</summary>
+## </param>
+#
+interface(`logging_startstop_syslog',`
+	gen_require(`
+		type syslogd_unit_t;
+		class service { start stop };
+	')
+	allow $1 syslogd_unit_t:service { start stop };
+')
+
 ########################################
 ## <summary>
 ##	Allow specified domain to check status of syslog unit