Fix pep8 violations in message/tlv.py
Fix pep8 violations in message/tlv.py

Change-Id: Ib1e60db32a2aaa2e9da05fa2be4605bf16cc6033
Signed-off-by: Thanh Ha <09ea4d3a79c8bee41a16519f6a431f6bc0fd8d6f@linuxfoundation.org>

opendaylight/bgpcep,bigdataops/bgpcep,inocybe/odl-bgpcep,inocybe/odl-bgpcep,bigdataops/bgpcep