Fix memory leak in Ip4Config.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Samer El-Haj-Mahmoud <elhaj@hp.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Tian Feng <feng.tian@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg@16465 6f19259b-4bc3-4df7-8a09-765794883524