smb: client: fix race with concurrent opens in rename(2)

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix race with concurrent opens in rename(2) Besides sending the rename request to the server, the rename process also involves closing any deferred close, waiting for outstanding I/O to complete as well as marking all existing open handles as deleted to prevent them from deferring closes, which increases the race window for potential concurrent opens on the target file. Fix this by unhashing the dentry in advance to prevent any concurrent opens on the target.