[Session] Work with PD and Fix empty continuations (#39038)

Co-authored-by: Byron Hsu <byron+per@periodiclabs.ai>
Co-authored-by: Manik Singhal <3400497+Manikvsin@users.noreply.github.com>

test/registered/unit/mem_cache/test_session_token_share_unit.py

@@ -43,6 +43,11 @@ def _recv(rid, input_ids, max_new_tokens=8):
         return_hidden_states=False,
         return_routed_experts=False,
         routed_experts_start_len=0,
+        bootstrap_host=None,
+        bootstrap_port=None,
+        bootstrap_room=None,
+        routed_dp_rank=None,
+        disagg_prefill_dp_rank=None,
         priority=None,
         routing_key=None,
         extra_key=None,