Make sure to initialize the the {do|is}_gzip variables to zero

before we start setting them otherwise.

bin/varnishd/cache_center.c

@@ -1153,6 +1153,11 @@ cnt_recv(struct sess *sp)
 		return (0);
 	}
 
+	sp->wrk->is_gzip = 0;
+	sp->wrk->is_gunzip = 0;
+	sp->wrk->do_gzip = 0;
+	sp->wrk->do_gunzip = 0;
+
 	if (params->http_gzip_support &&
 	     (recv_handling != VCL_RET_PIPE) &&
 	     (recv_handling != VCL_RET_PASS)) {

bin/varnishtest/tests/r00861.vtc

@@ -36,6 +36,8 @@ varnish v1 \
 client c1 {
 	txreq -url "/1"
 	rxresp
+	expect resp.http.Content-Encoding == resp.http.Content-Encoding
+	expect resp.bodylen == 22
 
 	txreq -url "/barf" -hdr "Accept-Encoding: gzip"
 	rxresp