MINOR: log: add time second fraction field to rfc5424 log timestamp.

This patch adds the time second fraction in microseconds
as supported by the rfc.
diff --git a/src/sink.c b/src/sink.c
index e3eac2b..19a555e 100644
--- a/src/sink.c
+++ b/src/sink.c
@@ -182,7 +182,7 @@
         }
 	else if (sink->fmt == SINK_FMT_RFC5424) {
 		pfx[npfx].ptr = logheader_rfc5424;
-                pfx[npfx].len = update_log_hdr_rfc5424(date.tv_sec) - pfx[npfx].ptr;
+		pfx[npfx].len = update_log_hdr_rfc5424(date.tv_sec, date.tv_usec) - pfx[npfx].ptr;
 		log_format = LOG_FORMAT_RFC5424;
 	}
 	else {