ocfs2/dlm: Retract fix for race between purge and migrate

Mainline commit d4f7e650

 attempts to delay
the dlm_thread from sending the drop ref message if the lockres is being
migrated. The problem is that we make the dlm_thread wait for the migration
to complete. This causes a deadlock as dlm_thread also participates in the
lockres migration process.

A better fix for the original oss bugzilla#1012 is in testing.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Acked-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>