PROTON-2476: Restore truncation behaviour for transfer frame traces
PROTON-2476: Restore truncation behaviour for transfer frame traces

The logging changes that came with PROTON-2448 had the side effect of no
longer truncating the message payloads that came along with transfer
frames.

This meant that these trace lines could get extremely long if applications
were sending long messages and could also take a very long time to allocate
memory and format the string.

gemmellr/qpid-proton,astitcher/qpid-proton,apache/qpid-proton,astitcher/qpid-proton,gemmellr/qpid-proton,apache/qpid-proton,apache/qpid-proton,apache/qpid-proton,gemmellr/qpid-proton,gemmellr/qpid-proton,apache/qpid-proton,astitcher/qpid-proton,astitcher/qpid-proton,gemmellr/qpid-proton,apache/qpid-proton,astitcher/qpid-proton,gemmellr/qpid-proton,astitcher/qpid-proton