[cluster-test] Terminate ct on SIGHUP
[cluster-test] Terminate ct on SIGHUP

When ssh connection terminated, process receives SIGHUP
We want to terminate ct at this point to make sure when circle job is cancelled we no longer keep cluster test session running.

Closes: #1976
Approved by: sausagee

libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core