fix r3756: release lock to allow other process to delete cache node
patch by Maxim Dounin

src/http/ngx_http_file_cache.c

diff --git a/src/http/ngx_http_file_cache.c b/src/http/ngx_http_file_cache.c
index 03cd268..f44fe1d 100644
--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c
@@ -1099,7 +1099,8 @@
         }
 
         if (fcn->deleting) {
-            continue;
+            wait = 1;
+            break;
         }
 
         p = ngx_hex_dump(key, (u_char *) &fcn->node.key,