Changes

testsuites: tunend: trex: configure.sh: Use trex binary depending on host

gtplab* hosts worked fine with regular t-rex-64 binary, but c240-* and
epyc1 segfault when starting it, probably due to use of AVX in the
locally compiled binary. On those hosts, use t-rex-64-o binary instead,
which doesn't contain such optimizations and hence doesn't segfault.

Change-Id: Ia50f37e193c1cf6a89b46a815a4c5ca54dbfe576