Java Generator problem with trimPayload in MAVLinkPacket.java

The trim payload function should just remove trailing zeros when encoding. Unfortunately it causes the packets to not be parsed correctly (I get the parse state MAVLINK_PARSE_STATE_GOT_BAD_CRC1) by the C++ mavlink parser on the other side. When I comment the function out, everything works ok.

I am using release/kinetic/mavlink branch
BUG:
Solution:
In mavgen_java.py -> Change len to payloadSize.

Reason:
When the payload gets trimmed, the actual length is reduced. Here we just used the original length when calculating CRC, therefore giving us a crc mismatch on the other side.