[master] 865df54a9 Revert "Remove a racy assert"

[Martin Blix Grydeland]

commit 865df54a92f120e234147ceabc7bd76cb7918868
Author: Martin Blix Grydeland <martin at varnish-software.com>
Date:   Fri Apr 26 13:45:21 2019 +0200

    Revert "Remove a racy assert"
    
    This reverts commit 462eab25381ccfd914be4b406e46d0441257f06f.
    
    That assert was there for a good reason.

diff --git a/bin/varnishd/cache/cache_fetch.c b/bin/varnishd/cache/cache_fetch.c
index 0dc8c3697..63738e1fe 100644
--- a/bin/varnishd/cache/cache_fetch.c
+++ b/bin/varnishd/cache/cache_fetch.c
@@ -980,6 +980,9 @@ VBF_Fetch(struct worker *wrk, struct req *req, struct objcore *oc,
 			(void)VRB_Ignore(req);
 		} else {
 			ObjWaitState(oc, BOS_STREAM);
+			if (oc->boc->state == BOS_FAILED) {
+				AN((oc->flags & OC_F_FAILED));
+			}
 		}
 	}
 	AZ(bo);