Improve stability of these two testcases.

We have to restart the server instance when we have writes which
might fail.

bin/varnishtest/tests/r00942.vtc

 varnishtest "#942 junk after gzip from backend"
 
-server s1 -repeat 2 {
+server s1 {
 	rxreq
 	txresp -nolen \
 		-hdr "Content-Encoding: gzip" \
@@ -18,13 +18,9 @@ server s1 -repeat 2 {
 		sendhex "00000000"
 		sendhex "00000000"
 	send "\r\n"
-
 	chunked "FOOBAR"
-
 	non-fatal
 	chunkedlen 0
-	accept
-	fatal
 } -start
 
 varnish v1 \
@@ -46,6 +42,31 @@ client c1 {
 	expect resp.status == 503
 } -run
 
+server s1 -wait {
+	fatal
+	rxreq
+	txresp -nolen \
+		-hdr "Content-Encoding: gzip" \
+		-hdr "Connection: close" \
+		-hdr "Transfer-Encoding: Chunked"
+	send "14\r\n"
+		# An empty gzip file:
+		sendhex "1f8b"
+		sendhex "08"
+		sendhex "00"
+		sendhex "00000000"
+		sendhex "00"
+		sendhex "03"
+		sendhex "0300"
+		sendhex "00000000"
+		sendhex "00000000"
+	send "\r\n"
+	chunked "FOOBAR"
+	non-fatal
+	chunkedlen 0
+} -start
+
+
 client c1 {
 	txreq -url /2 -hdr "Foo: foo"
 	rxresp

bin/varnishtest/tests/r01086.vtc

@@ -22,11 +22,30 @@ server s1 {
 
 	delay .2
 
-	non-fatal
 	chunked "FOOBAR"
+	non-fatal
 	chunkedlen 0
+} -start
+
+
+varnish v1 -vcl+backend {
+	sub vcl_backend_response {
+		if (beresp.http.set-cookie == "BAR") {
+			set beresp.do_stream = false;
+		}
+	}
+} -start
+
+client c1 {
+	txreq -hdr "Cookie: FOO"
+	rxresphdrs
+	expect resp.status == 200
+	expect_close
+} -run
+
+delay .1
 
-	accept
+server s1 -wait {
 	fatal
 
 	# This one will not be streamed
@@ -50,31 +69,12 @@ server s1 {
 
 	delay .2
 
-	non-fatal
 	chunked "FOOBAR"
+	non-fatal
 	chunkedlen 0
 
-	accept
-
-} -start
-
-varnish v1 -vcl+backend {
-	sub vcl_backend_response {
-		if (beresp.http.set-cookie == "BAR") {
-			set beresp.do_stream = false;
-		}
-	}
 } -start
 
-client c1 {
-	txreq -hdr "Cookie: FOO"
-	rxresphdrs
-	expect resp.status == 200
-	expect_close
-} -run
-
-delay .1
-
 client c1 {
 	txreq -hdr "Cookie: BAR"
 	rxresp