LU-4209 utils: fix O_TMPFILE/O_LOV_DELAY_CREATE conflict

LU-4209 utils: fix O_TMPFILE/O_LOV_DELAY_CREATE conflict

In kernel 3.11 O_TMPFILE was introduced, but the open flag value
conflicts with the O_LOV_DELAY_CREATE flag 020000000 added to fix
LU-812 in Lustre 2.4.  O_LOV_DELAY_CREATE allows applications
to defer file layout and object creation from open time (the default)
until it can instead be specified by the application using an ioctl.

Instead of trying to find a non-conflicting O_LOV_DELAY_CREATE flag
or define a Lustre-specific flag that isn't of use to most/any other
filesystems, use (O_NOCTTY|FASYNC) as the new value.  These flags
are not meaningful for newly-created regular files and should be
ok since O_LOV_DELAY_CREATE is only meaningful for new files.

I looked into using O_ACCMODE/FMODE_WRITE_IOCTL, which allows calling
ioctl() on the minimally-opened fd and is close to what is needed,
but that doesn't allow specifying the actual read or write mode for
the file, and fcntl(F_SETFL) doesn't allow O_RDONLY/O_WRONLY/O_RDWR
to be set after the file is opened.

We will keep the 0100000000 flag for backward compatibility until
3.13 is the oldest client kernel that is supported, but drop the
conflicting __O_TMPFILE value of 02000000 since that will cause an
error when running on newer kernels.  The 020000000 has only been
used since Lustre 2.4.0 and always in conjunction with 0100000000,
so any apps that used O_LOV_DELAY_CREATE directly instead of calling
llapi_file_create*() will still work until Linux 3.13 is used.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I565f3454616edc60c6acee01034aa5d773500c1e
Reviewed-on: http://review.whamcloud.com/8312
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Peng Tao <bergwolf@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>