Restore running xacts from CLOG on replica startup

pageserver/src/walingest.rs

@@ -373,6 +373,7 @@ impl WalIngest {
                 if info == pg_constants::XLOG_RUNNING_XACTS {
                     let xlrec = crate::walrecord::XlRunningXacts::decode(&mut buf);
                     self.checkpoint.oldestActiveXid = xlrec.oldest_running_xid;
+                    self.checkpoint_modified = true;
                 }
             }
             _x => {

test_runner/regress/test_replication_start.py

@@ -1,9 +1,7 @@
-import pytest
 from fixtures.log_helper import log
 from fixtures.neon_fixtures import NeonEnv, wait_replica_caughtup
 
 
-@pytest.mark.xfail
 def test_replication_start(neon_simple_env: NeonEnv):
     env = neon_simple_env