[201811] Fix: not to use blocking get_all() after keys(), if routestr does not exist, skip#258

qiluo-msft merged 2 commits intosonic-net:201811sonic-net/sonic-snmpagent:201811from

qiluo-msft:qiluo/noblockkey2018qiluo-msft/sonic-snmpagent:qiluo/noblockkey2018Copy head branch name to clipboard