ping works but telnet fail

在多网卡的情况，ping发出和回复可以在不同的网口。但是telnet必须要求同一个网口

Find one UE can telnet but telnet fail. Also fail to open TL1(oam interface). 

Becuase telnet successful from same subnet, find root cause is routing table.

root cause:

ping can reply from another interface, and it would work, but telnet can only work with same interface.