CID 455002: Error handling issues in lib/isc/loop.c

I think this Coverity Scan issue was triggered by adding two uv_async_send() calls in 7b1d985d that check return values, so Coverity thinks we might want to check uv_async_send()s return value elsewhere as well:

/lib/isc/loop.c: 483 in isc_loopmgr_pause()
477     
478     		/* Skip current loop */
479     		if (i == isc_tid()) {
480     			continue;
481     		}
482     
>>>     CID 455002:  Error handling issues  (CHECKED_RETURN)
>>>     Calling "uv_async_send" without checking return value (as is done elsewhere 5 out of 6 times).
483     		uv_async_send(&loop->pause_trigger);
484     	}
485     
486     	RUNTIME_CHECK(atomic_compare_exchange_strong(&loopmgr->paused,
487     						     &(bool){ false }, true));
488     	pause_loop(CURRENT_LOOP(loopmgr));

For your consideration @fanf.