cifs: eliminate some more premature cifsd exits

If the tcpStatus is still CifsNew, the main cifs_demultiplex_loop can
break out prematurely in some cases. This is wrong as we will almost
always have other structures with pointers to the TCP_Server_Info. If
the main loop breaks under any other condition other than tcpStatus ==
CifsExiting, then it'll face a use-after-free situation.

I don't see any reason to treat a CifsNew tcpStatus differently than
CifsGood. I believe we'll still want to attempt to reconnect in either
case. What should happen in those situations is that the MIDs get marked
as MID_RETRY_NEEDED. This will make CIFSSMBNegotiate return -EAGAIN, and
then the caller can retry the whole thing on a newly reconnected socket.
If that fails again in the same way, the caller of cifs_get_smb_ses
should tear down the TCP_Server_Info struct.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>