MINOR: config/mux-h2: Return ERR_ flags from init_h2() instead of a status

post-check function callbacks must return ERR_* flags. Thus, init_h2() is fixed
to return ERR_NONE on success or (ERR_ALERT|ERR_FATAL) on error.

This patch may be backported as far as 2.2.

(cherry picked from commit 5214099233d99b8288fb392dfe911bc9ea86e9af)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 740e255..482c620 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -6398,9 +6398,11 @@
 	pool_head_hpack_tbl = create_pool("hpack_tbl",
 	                                  h2_settings_header_table_size,
 	                                  MEM_F_SHARED|MEM_F_EXACT);
-	if (!pool_head_hpack_tbl)
-		return -1;
-	return 0;
+	if (!pool_head_hpack_tbl) {
+		ha_alert("failed to allocate hpack_tbl memory pool\n");
+		return (ERR_ALERT | ERR_FATAL);
+	}
+	return ERR_NONE;
 }
 
 REGISTER_POST_CHECK(init_h2);