NetworkPkg/DnsDxe: Update RetryCount/RetryInterval to comply with UEFI spec.

NetworkPkg/DnsDxe: Update RetryCount/RetryInterval to comply with UEFI spec.

According to UEFI spec:
"Retry number if no response received after RetryInterval. If zero, use
the parameter configured through Dns.Configure() interface."
"Minimum interval of retry is 2 second. If the retry interval is less
than 2 second, then use the 2 second. If zero, use the parameter configured
through Dns.Configure() interface."

For both DNS.HostNameToIp and DNS.GeneralLookUp, the value of RetryCount /
RetryInterval need to be updated to comply with UEFI spec.

Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Wang Fan <fan.wang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>