REG-TESTS: cache: Remove T-E header for 304-Not-Modified responses

VTEST does not properly handle 304-Not-Modified responses. If a
Transfer-Encoding header (and probably a Content-Lenght header too), it
waits for a body. Waiting for a fix, the Transfer-Encoding encoding of
cached responses in 2 VTEST scripts are removed.

Note it is now an issue because of a fix in the H1 multiplexer :

  * 226082d13a "BUG/MINOR: mux-h1: Do not send a last null chunk on body-less answers"

This patch must be backported with the above commit.

reg-tests/cache/if-modified-since.vtc

@@ -61,6 +61,10 @@ haproxy h1 -conf {
                server www ${s1_addr}:${s1_port}
                http-response cache-store my_cache
 
+               # Remove Transfer-Encoding header because of a vtest issue with
+               # 304-Not-Modified responses
+               http-after-response del-header transfer-encoding if { status eq 304 }
+
        cache my_cache
                total-max-size 3
                max-age 20
@@ -148,4 +152,3 @@ client c1 -connect ${h1_fe_sock} {
        expect resp.bodylen == 0
 
 } -run
-

reg-tests/cache/if-none-match.vtc

@@ -46,6 +46,10 @@ haproxy h1 -conf {
                server www ${s1_addr}:${s1_port}
                http-response cache-store my_cache
 
+               # Remove Transfer-Encoding header because of a vtest issue with
+               # 304-Not-Modified responses
+               http-after-response del-header transfer-encoding if { status eq 304 }
+
        cache my_cache
                total-max-size 3
                max-age 20