quota: be aware of error from dquot_initialize

Commit 6184fc0b

 ("quota: Propagate error from ->acquire_dquot()")
missed to handle error from dquot_initialize in dquot_file_open, fix it.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>