LU-6205 tests: fix bash expansion of fid

LU-6205 tests: fix bash expansion of fid

When calling lfs path2fid, the FID is returned between bracket. When
that fid variable is used, it may be expanded by the shell to
something else. For instance:

  $ touch x
  $ ../utils/lfs fid2path lustre [0x200000be7:0xb:0x0]
  bad FID format [x], should be [0x1:0x2:0x0]

  fid2path: error on FID x: Invalid argument

This will cause some tests, like 154A or 238, to sometimes fail.

Use quotes where the FIDs are used.

Replace "$(lfs ..." with "$($LFS ..." and made a couple variables
local.

Signed-off-by: frank zago <fzago@cray.com>
Change-Id: I3c1a34585ebaa596d66063f5ada3ccfc4d202ade
Reviewed-on: http://review.whamcloud.com/13618
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>