lustre module uses a deprecated lustre_user

On newer Lustre versions, Darshan spits out the following:

In file included from lib/darshan-lustre.c(21):
/usr/include/lustre/lustre_user.h(45): warning #1224: #warning directive: "Including lustre_user.h is deprecated. Include linux/lustre/lustre_user.h directly."
  #warning "Including lustre_user.h is deprecated. Include linux/lustre/lustre_user.h directly."
   ^

Simple fix, but needs to be done. Probably by me.