s3:vfs_gpfs:Fix query of creation time from GPFS
Setting the creation time through SetFileTime on a GPFS file system and
querying it with GetFileTime shows a mismatch.
The vfs_gpfs module first retrieves the information from the operating
system and the flag st_ex_calculated_birthtime is set to false. When
vfs_gpfs retrieves the birthtime from GPFS the flag
st_ex_calculated_birthtime has to be set to true. Otherwise the birth
time will get overwritten by a call to update_stat_ex_mtime, reporting
the wrong time to a client system.
Signed-off-by: Christian Ambach <ambi@samba.org>