LU-3606 fallocate: Implement fallocate preallocate operation

LU-3606 fallocate: Implement fallocate preallocate operation

This patch adds fallocate(2) preallocate operation support
for Lustre. fallocate(2) method of the inode_operations or
file_operations is implemented and transported to the OSTs
to interface with the underlying OSD's fallocate(2) code.

In a saperate patch, a new RPC, OST_FALLOCATE has been
added and reserved for space preallocation. The fallocate
functionality (prealloc) in CLIO has been multiplexed
with CIT_SETATTR. (https://review.whamcloud.com/37277)

Lustre fsx(File system exerciser) is updated in a saperate
patch to handle fallocate calls. (https://review.whamcloud.com/37277)

Only fallocate preallocate operation is supported by this
patch for now. Other operations like, FALLOC_FL_PUNCH
(deallocate), FALLOC_FL_ZERO_RANGE, FALLOC_FL_COLLAPSE_RANGE
and FALLOC_FL_INSPECT_RANGE is not supported by this patch
and will be addressed by a separate patch.

ZFS operation is not supported by this patch. ZFS fallocate(2)
will be addressed by patch (https://review.whamcloud.com/36506/)

New test case under sanity is added to verify fallocate
call.

Test-Parameters: fstype=ldiskfs testlist=sanity,sanityn,sanity-dom
Signed-off-by: Swapnil Pimpale <spimpale@ddn.com>
Signed-off-by: Li Xi <lixi@ddn.com>
Signed-off-by: Abrarahmed Momin <abrar.momin@gmail.com>
Signed-off-by: Arshad Hussain <arshad.super@gmail.com>
Change-Id: I03f27d356616fbf3a3ab8e6309af26c00434d81b
Reviewed-on: https://review.whamcloud.com/9275
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>