api: adjust the behavior of header's present_match (#16627)

Currently, envoy ignores the value of present match. This commit adjust
envoy's behavior. When the value is True, envoy will check the header
present. When the value is False, envoy will check the header absent.

Signed-off-by: He Jie Xu <hejie.xu@intel.com>

Mirrored from https://github.com/envoyproxy/envoy @ 9a7a7ede474780c2bd8fe59e7a93e537204cfe31

envoy/config/route/v3/route_components.proto

@@ -1885,8 +1885,8 @@ message HeaderMatcher {
     //   "-1somestring"
     type.v3.Int64Range range_match = 6;
 
-    // If specified, header match will be performed based on whether the header is in the
-    // request.
+    // If specified as true, header match will be performed based on whether the header is in the
+    // request. If specified as false, header match will be performed based on whether the header is absent.
     bool present_match = 7;
 
     // If specified, header match will be performed based on the prefix of the header value.

envoy/config/route/v4alpha/route_components.proto

@@ -1837,8 +1837,8 @@ message HeaderMatcher {
     //   "-1somestring"
     type.v3.Int64Range range_match = 6;
 
-    // If specified, header match will be performed based on whether the header is in the
-    // request.
+    // If specified as true, header match will be performed based on whether the header is in the
+    // request. If specified as false, header match will be performed based on whether the header is absent.
     bool present_match = 7;
 
     // If specified, header match will be performed based on the prefix of the header value.