network: append period if error message provided by kernel does not contain it

Author: yuwata

src/network/networkd-link.c

@@ -4305,5 +4305,10 @@ int log_link_message_full_errno(Link *link, sd_netlink_message *m, int level, in
         const char *err_msg = NULL;
 
         (void) sd_netlink_message_read_string(m, NLMSGERR_ATTR_MSG, &err_msg);
-        return log_link_full(link, level, err, "%s: %s%s%m", msg, strempty(err_msg), err_msg ? " " : "");
+        return log_link_full(link, level, err,
+                             "%s: %s%s%s%m",
+                             msg,
+                             strempty(err_msg),
+                             err_msg && !endswith(err_msg, ".") ? "." : "",
+                             err_msg ? " " : "");
 }