[CIFS] Reduce CIFS tcp congestion timeout (it was too long) and backoff

ever longer amounts (up to 15 seconds).  This improves performance
especially when using large wsize.

Signed-off-by: Steve French (sfrench@us.ibm.com)

diff --cc fs/cifs/cifs_debug.c
Simple merge

diff --cc fs/cifs/cifsfs.c
Simple merge

diff --cc fs/cifs/transport.c
Simple merge