Do not send JDWP data in case of error.

Do not send JDWP data in case of error.

When sending JDWP reply packet with an error, we want to ignore any data in the
buffer. While we reflect that in the packet's length (first 4 bytes), we used
to send all data in the buffer. This causes the receiver to read malformed JDWP
packet.

This CL adds "length" argument to JdwpNetStateBase::WritePacket so we control
the amount of data we send. If the reply has no error, it is set to the length
of the buffer. Otherwise it is the length of JDWP packet header indicating no
data is available.

Bug: 13366758
Change-Id: Ib72c10d5faf065fb44901c34b2732496b6667efa