[master] 91822c85e assert umem cache sanity

[Nils Goroll]

commit 91822c85e1717033df16fd2302ecd75fcb8b7694
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Feb 5 09:37:54 2020 +0100

    assert umem cache sanity
    
    Ref #3210

diff --git a/bin/varnishd/storage/storage_umem.c b/bin/varnishd/storage/storage_umem.c
index db45305f6..bc3458e9c 100644
--- a/bin/varnishd/storage/storage_umem.c
+++ b/bin/varnishd/storage/storage_umem.c
@@ -201,6 +201,11 @@ smu_alloc(const struct stevedore *st, size_t size)
 	}
 	smu->sz = size;
 	smu->s.space = size;
+#ifndef BUG3210
+	assert(smu->sc == smu_sc);
+	assert(smu->s.priv == smu);
+	AZ(smu->s.len);
+#endif
 	return (&smu->s);
 }