bcache: fix waiting problem for completed IO

Call _wait_all() which does check whether there is still
some pending IO before sleep. Otherwise it may happen
our submitted IO operations have been already dispatched
and this call then endlessly waits for IO which are all done.
This can be reproduced when device returns quickly errors
on write requests.

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.03.11 - 
 ==================================
+  Fix bcache waiting for IO completion with failing disks.
   Configure use own python path name order to prefer using python3.
   Add configure --enable-editline support as an alternative to readline.
   Enhance reporting and error handling when creating thin volumes.

lib/device/bcache.c

@@ -963,7 +963,7 @@ static struct block *_new_block(struct bcache *cache, int di, block_address i, b
 			if (can_wait) {
 				if (dm_list_empty(&cache->io_pending))
 					_writeback(cache, 16);  // FIXME: magic number
-				_wait_io(cache);
+				_wait_all(cache);
 			} else {
 				log_debug("bcache no new blocks for di %d index %u",
 					  di, (uint32_t) i);