Fixed XMPPIncomingFileTransfer stucks on state XMPPIFTStateWaitingForSIOffer

[poca-p0ca]

fixed XMPPIncomingFileTransfer stucks on state XMPPIFTStateWaitingForSIOffer when receiving disco#info result while client is sending a file.

if XMPPOutgoingFileTransfer and XMPPIncomingFileTransfer are both activated, XMPPOutgoingFileTransfer sends disco#info request to recipient client, and when recipient returns disco#info result, client's XMPPIncomingFileTransfer sends disco#info identity and makes its state to XMPPIFTStateWaitingForSIOffer.

if ((_transferState == XMPPIFTStateNone) && [self isDiscoInfoIQ:iq]) {
    [self sendIdentity:iq];
    _transferState = XMPPIFTStateWaitingForSIOffer;
      
      return YES;
  }

Since -isDiscoInfoIQ: doesn't checks whether it's a result or request or something, unless disco#info iq was result, -isDiscoInfoIQ: will return true.

So unless XMPPStream receives disco#info request, XMPPIncomingfileTransfer's state is not a XMPPIFTStateNone, so disco#info result will never be sended.

Therefore, it need to check whether it's a result or request, I implemented some codes which checks the iq message's state.

if ((_transferState == XMPPIFTStateNone) && [self isDiscoInfoIQ:iq]) {
    if ([iq type] != @"result" || [[iq elementForName:@"query"] elementForName:@"identity"] == nil) {
      [self sendIdentity:iq];
      _transferState = XMPPIFTStateWaitingForSIOffer;
      
      return YES;
    }
  }