tfork: add a suppresssions file for drd

tfork: add a suppresssions file for drd

drd reports:

 initialized twice: cond 0x514f188
    at 0x4C3A399: pthread_cond_init_intercept (drd_pthread_intercepts.c:1022)
    by 0x4C3A399: pthread_cond_init@* (drd_pthread_intercepts.c:1030)
    by 0x50F3FF3: tfork_atfork_child (tfork.c:250)
    by 0x9A4B95D: fork (fork.c:204)
    by 0x50F4834: tfork_start_waiter_and_worker (tfork.c:581)
    by 0x50F4CDB: tfork_create (tfork.c:780)
    by 0x2F7469: tfork_thread (tfork.c:431)
    by 0x4C358F8: vgDrd_thread_wrapper (drd_pthread_intercepts.c:444)
    by 0x8D46593: start_thread (pthread_create.c:463)
    by 0x9A7EE6E: clone (clone.S:95)
 cond 0x514f188 was first observed at:
    at 0x4C3A399: pthread_cond_init_intercept (drd_pthread_intercepts.c:1022)
    by 0x4C3A399: pthread_cond_init@* (drd_pthread_intercepts.c:1030)
    by 0x50F413A: tfork_global_initialize (tfork.c:287)
    by 0x8D4DEA6: __pthread_once_slow (pthread_once.c:116)
    by 0x4C377FD: pthread_once_intercept (drd_pthread_intercepts.c:800)
    by 0x4C377FD: pthread_once (drd_pthread_intercepts.c:806)
    by 0x50F4C0E: tfork_create (tfork.c:743)
    by 0x2F7469: tfork_thread (tfork.c:431)
    by 0x4C358F8: vgDrd_thread_wrapper (drd_pthread_intercepts.c:444)
    by 0x8D46593: start_thread (pthread_create.c:463)
    by 0x9A7EE6E: clone (clone.S:95)

This is intentional, the reinit is in a child process. Cf the comment in
tfork.c.

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>