Revert "drops suplemental groups when droping privileges."

This reverts commit 634ccba7c3f9f72f7aedbe4690c18ebdbdf8b2e1.

doesn't work on OSX for some reason

gunicorn/util.py

@@ -146,9 +146,6 @@ def set_owner_process(uid,gid):
             # groups like on osx or fedora
             os.setgid(-ctypes.c_int(-gid).value)
 
-        # Also drop supplemental groups
-        os.setgroups([])
-
     if uid:
         os.setuid(uid)