We don't want to break SMB sessions if we receive signals when
sending packets through the network. Fix it by masking off signals
inside __smb_send_rqst() to avoid partial packet sends due to
interrupts.

Return -EINTR if a signal is pending and only a part of the packet
was sent. Return a success status code if the whole packet was sent
regardless of signal being pending or not. This keeps a mid entry
for the request in the pending queue and allows the demultiplex
thread to handle a response from the server properly.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>