msg: fix bug with setfield(mpls)
msg: fix bug with setfield(mpls)

Signed-off-by: Stepanov Evgeniy <be3de3bd07bc0e6f7c7235242d1477827e7e64b3@arccn.ru>

ARCCN/libfluid_msg,OpenNetworkingFoundation/libfluid_msg,OpenNetworkingFoundation/libfluid_msg,OpenNetworkingFoundation/libfluid_msg,ARCCN/libfluid_msg,ARCCN/libfluid_msg