Duplicate the device path prior to the access to it
[Impaction]
directly access the device path may cause an exception when the device path includes some unaligned device path nodes
[Reference Info]
In the case of ISCSI, there is a situation that the device path may consists of some unaligned device path node. it causes the unaligned exception when we access the node.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4905 6f19259b-4bc3-4df7-8a09-765794883524