core: use uniform style for RateLimit initialization

RateLimit is designed so that we can always initialize only the first two
fields explicitly. All other call sites use a single line for this.

src/core/path.c

@@ -279,8 +279,7 @@ static void path_init(Unit *u) {
 
         p->directory_mode = 0755;
 
-        p->trigger_limit.interval = USEC_INFINITY;
-        p->trigger_limit.burst = UINT_MAX;
+        p->trigger_limit = RATELIMIT_OFF;
 }
 
 void path_free_specs(Path *p) {