ocfs2: Remove ocfs2_dquot_initialize() and ocfs2_dquot_drop()

Since ->acquire_dquot and ->release_dquot callbacks aren't called under
dqptr_sem anymore, we don't have to start a transaction and obtain locks
so early. So we can just remove all this complicated stuff.

Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mark Fasheh <mfasheh@suse.de>