cifs: Fix error in smb_send2

Backport of upstream commit 61de800d33af585cb7e6f27b5cdd51029c6855cb
for -stable.

[CIFS] fix error in smb_send2

smb_send2 exit logic was strange, and with the previous change
could cause us to fail large
smb writes when all of the smb was not sent as one chunk.

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Cc: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>