GMPLS update - 39: adding out-segment interface index

Added #mpls-interface based #indexing on #out-segment configuration entries in GMPLS module. This will help in doing #search #operations among the out-segment entries for #specific #interfaces in a #quick and #efficient manner. On #interface #changes the events are #forwarded to all the segments created on the interface. From segments the events will be #chained to #cross-connects and then further to the parent #tunnel #LSPs. On maintaining the interface index on segments expedite the event chaining process. The mpls-interface is used as an index in to the segment.

#GMPLS update 39 ...
[commit 6eb7fdc4ff93043e82a02accd2e5ea7152df5757] (https://github.com/nes-repo/NES-Open-Switch/commit/6eb7fdc4ff93043e82a02accd2e5ea7152df5757)