Msgpack int/uint interoperation problem in kafka-mdm input

[itaiin]

When sending metrics to MetricTank using kafka-mdm with certain msgpack clients, one may get the error

kafka-mdm decode error, skipping message. msgp: attempted to decode type "uint" with method for "int"

This is because it is common practice in many msgpack clients to use int and uint interchangeably (for example in msgpack-python positives are encoded as uint and negatives as int).

Fortunately, this issue was seems also to be fixed in newer versions of tinylib/msgp so only an update is needed.

[Dieterbe]

ok we can probably fix this by upgrading our msgp library. something for the change window of the next release

[Dieterbe]

this will also allow us to remove this hack:
84daa62