EX-4015 lipe: use direct IO

EX-4015 lipe: use direct IO

Use direct IO by default in lipe_scan3. Retry ext2fs_open() without
EXT2_FLAG_DIRECT_IO if it fails. Add a --direct-io=0|1 option to
explicitly disable or enable direct IO.

Add an --io-options option to pass down ext2 io_manager options.

Test-Parameters: trivial testlist=sanity-lipe-find3 serverextra_install_params="--packages lipe-scan"
Test-Parameters: trivial testlist=sanity-lipe-scan3 serverextra_install_params="--packages lipe-scan" facet=mds1
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I25347949bbff9e697da26431807daf37cfb720fa
Reviewed-on: https://review.whamcloud.com/46682
Tested-by: jenkins <devops@whamcloud.com>