LU-14677 sec: remove MIGRATION_ compatibility defines

LU-14677 sec: remove MIGRATION_ compatibility defines

Remove the MIGRATION_* compatibility flags and use
LLAPI_MIGRATION_* everywhere.

Test-Parameters: trivial
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Iab2a2f6dfc435377e9db0d4963547841b2cbc403
Reviewed-on: https://review.whamcloud.com/44957
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>