Make sandesh_trace_dump.py compatible with python 2.x and 3.x
Make sandesh_trace_dump.py compatible with python 2.x and 3.x

Presently, sandesh_trace_dump.py utility doesn't work with python 3.x as
some functions used in the script either does not exist or syntax of which has
changed in python 3.x
Modified sandesh_trace_dump.py to work with both python 2.x and 3.x

Change-Id: I80d18ecbd26a0f990d9eb68ae2cf390a2574b85a
Closes-Bug:#1399478

toabctl/contrail-sandesh,Juniper/contrail-sandesh,toabctl/contrail-sandesh,toabctl/contrail-sandesh,safchain/contrail-sandesh,safchain/contrail-sandesh,Juniper/contrail-sandesh,safchain/contrail-sandesh,Juniper/contrail-sandesh,toabctl/contrail-sandesh,Juniper/contrail-sandesh,safchain/contrail-sandesh