GMPLS update - 70: updating custom label-stack agent mapper routines

Updated #custom #label-stack agent mapper routines in GMPLS module. The agent #iterator routines and #mapper #routine has been updated to use standard #label-stack entry based #indexing. This will access the label-stack entries by using the #native #indexing. This removes references to the custom label-stack indexing used earlier. This will reduce the memory requirement associated with the custom label-stack entries. The custom label-stack #entries add support for #label-stack #attributes like GMPLS #label-type and #label-value, etc ...

#GMPLS update 70 ...
[commit 48da86fd34b3d887109f1759c4120340e02cd808] (https://github.com/nes-repo/NES-Open-Switch/commit/48da86fd34b3d887109f1759c4120340e02cd808)