Fix compilation with samba release > 4.1.4 - use new API functions
introduced to access opaque assoc_group_id

(cherry picked from commit 73a49af50bf0a496cfe62f49e60a662f1d04d685)
Remove 4.1.4 limitation when running make samba-git

(cherry picked from commit acd0c87442a4a71062eead51e20ac6a4a76e8e11)