xfs/133,4: make sure xfs_db sets negative i_size

xfs/133,4: make sure xfs_db sets negative i_size

1) xfs/133 and xfs/134 work abnornamlly on RHEL6.8GA and RHEL6.9Beta
   because xfs_db fails to set negative i_size and reports "usage:
   write fieldname value".  The special argument "--" is only used to
   end option-scanning in getopt().  So we can run two xfs_db commands
   to set negative i_size regardless of the special argument "--" is
   needed or not.  getopt() has been produced by 'commit c9f5e3db22098
   ("xfs_db: Allow writes of corrupted data")'.

2) xfs/134 passes unexpectedly on RHEL6.8GA due to EINVAL, so we use
   touch command to create 512-aligned test file.

Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>