Ignore flaky metrics tests on CI (#832)

Fixes #831.

Proxy metrics tests `transport::inbound_tcp_accept` and `transport::inbound_tcp_duration` are known to be flaky and should be ignored on CI. Note that the outbound versions of these tests were already marked as flaky, so this was almost certainly either an oversight or the result of an incorrect merge.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

proxy/tests/telemetry.rs

@@ -855,6 +855,7 @@ mod transport {
     }
 
     #[test]
+    #[cfg_attr(not(feature = "flaky_tests"), ignore)]
     fn inbound_tcp_accept() {
         let _ = env_logger::try_init();
         let TcpFixture { client, metrics, proxy: _proxy } =
@@ -887,7 +888,9 @@ mod transport {
             "tcp_accept_close_total{direction=\"inbound\",classification=\"success\"} 2");
     }
 
+    // https://github.com/runconduit/conduit/issues/831
     #[test]
+    #[cfg_attr(not(feature = "flaky_tests"), ignore)]
     fn inbound_tcp_duration() {
         let _ = env_logger::try_init();
         let TcpFixture { client, metrics, proxy: _proxy } =