Add support for TCP port reuse (same tuple6 but different ISN) in session manager: evict old session and create new session

include/stellar/session.h

@@ -44,11 +44,12 @@ enum flow_direction
 enum closing_reason
 {
     CLOSING_BY_TIMEOUT = 0x1,
-    CLOSING_BY_EVICTED = 0x2,
-    CLOSING_BY_CLIENT_FIN = 0x3,
-    CLOSING_BY_CLIENT_RST = 0x4,
-    CLOSING_BY_SERVER_FIN = 0x5,
-    CLOSING_BY_SERVER_RST = 0x6,
+    CLOSING_BY_LRU_EVICTED = 0x2,
+    CLOSING_BY_PORT_REUSE_EVICTED = 0x3,
+    CLOSING_BY_CLIENT_FIN = 0x4,
+    CLOSING_BY_CLIENT_RST = 0x5,
+    CLOSING_BY_SERVER_FIN = 0x6,
+    CLOSING_BY_SERVER_RST = 0x7,
 };
 
 enum session_stat