LU-12037 mdt: call mdt_dom_discard_data() after rename unlock

LU-12037 mdt: call mdt_dom_discard_data() after rename unlock

mdt_reint_rename() should drop all locks including global rename
lock, and then call mdt_dom_discard_data(), otherwise it may
cause deadlock.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I72cad3ee589c98c54f1e1281c39faa8779e562e8
Reviewed-on: https://review.whamcloud.com/34401
Tested-by: Jenkins
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Stephan Thiell <sthiell@stanford.edu>
Reviewed-by: Oleg Drokin <green@whamcloud.com>