LU-15045 utils: fix lfs_migrate for files with spaces

LU-15045 utils: fix lfs_migrate for files with spaces

Fix the lfs_migrate script to properly quote "$OLDNAME" so that
it works for filenames with spaces and other characters in them.

Lustre-change: https://review.whamcloud.com/45173
Lustre-commit: 0549031b991ec0bbf570a41c7d28b8a7fd4b41c3

Test-Parameters: trivial
Fixes: 8bedfa377fbd ("LU-11510 lfs: migrate a composite layout file correctly")
Fixes: 128137adfc53 ("LU-13090 utils: fix lfs_migrate -p for file with pool")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ic00f41f3a91ad9dfa491ff57768a3da0c6300c1e
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-on: https://review.whamcloud.com/46685
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>