valid user groups access denied after samba upgrade

Issue

• When using security = server without winbindd, samba version 3.6.23-14.el6_6 does not accept supplementary group membership for share access.
• An example of a configuration that will exhibit this problem:

[global]
        workgroup = EXAMPLE
        server string = Linux Samba Server %v
        interfaces = eth0
        security = SERVER
        password server = DC1
        client NTLMv2 auth = No
        client lanman auth = Yes
        max log size = 0
        debug pid = Yes
        load printers = No
        printcap name = /dev/printcap
        disable spoolss = Yes
        show add printer wizard = No
        dns proxy = No
        wins server = 192.168.1.150
        idmap config * : backend = tdb

[test]
        comment = test
        path = /test
        valid users = +testgroup
        read only = No
        create mask = 0775

# ls -lah /test/
total 8.0K
drwxrwxrwx.  2 root root 4.0K Apr  1 15:34 .
dr-xr-xr-x. 27 root root 4.0K May  6 14:59 ..

# id testuser3
uid=504(testuser3) gid=505(testuser3) groups=505(testuser3),503(testgroup)