SNMPTrap: SNMPTrap address support hostname

The address of snmptrap only supports IP(such as 192.168.1.1), not
support hostname(such as www.snmptrap.com). This commit enables the
snmptrap address to support hostname.

Tested:
1.Creat snmp trap client with hostname "snmp.prashanth.com" :
  busctl call xyz.openbmc_project.Network.SNMP
  /xyz/openbmc_project/network/snmp/manager
  xyz.openbmc_project.Network.Client.Create
  Client sq "snmp.prashanth.com" 162

  busctl introspect xyz.openbmc_project.Network.SNMP
  /xyz/openbmc_project/network/snmp/manager/1
  xyz.openbmc_project.Network.Client
  NAME     TYPE      SIGNATURE RESULT/VALUE
  .Address property  s         "snmp.prashanth.com"
  .Port    property  q         162

2.Create an error log, and then I received snmptrap on the computer
  with address "snmp.prashanth.com".

Signed-off-by: Chicago Duan <duanzhijia01@inspur.com>
Change-Id: I38e0963735036bf2bbaa102822f735345a3087d1
2 files changed